Playback device

ABSTRACT

A client ( 1 ) is provisioned with a content selection unit ( 13 ) for referencing description information ( 26 ), selecting content to be played in a certain period, and at the same time, and selecting content to be played at the next period from an id of a subset that is the same as the subset selected at the period, a request execution unit ( 14 ) for requesting the transmission of the selected content, and a content playback unit ( 15 ) for continuously playing the content transmitted in response to the request.

TECHNICAL FIELD

The present invention relates to a playback device or the like forplaying content acquired through a communication network, and morespecifically relates to a playback device that references a descriptioninformation including information related to the content and determinesthe content to acquire.

BACKGROUND ART

According to the related art, technologies for performing the supply ofcontent through a communication network are widely used. For example,PTL 1 below discloses a content streaming service system in whichcontent requests are transmitted from a client to a server by HTTP, andthe content received by the client as the response to this request isplayed as a stream.

A 3GPP AHS (Adaptive HTTP Streaming) is an example of such a system. Itis known that according to 3GPP AHS, description information (metadata)called MPD (Media Presentation Description) is used. Content (media)attributes, playback order, and so on are written in the MPD, and aresent to the client before the streaming service or during the streamingservice. Also, the client references the received MPD and determines thecontent to request to the server.

This MPD is written with periods (Period) representing time periods andrepresentations (Representation) representing content information to beplayed during these time periods. The MPD is data such as thatillustrated in FIG. 16, for example.

FIG. 16 is a diagram illustrating an example of the MPD according to therelated art. The MPD in FIG. 16 begins with <Period start=“PT0S”>,includes the period (element) ending by the </Period>, begins again withthe <Period start=“PT10S”>, and includes the period ending by the</Period>.

Also, three representations (elements) beginning with <Representation .. . > and ending with </Representation> are included in the periodbeginning with <Period start=“PT0S”>. In this way, the multiplerepresentations included in one period represent a selection of content.That is to say, the multiple representations included in the same periodindicate that any one of these may be selected for possible playback.

Also, each representation (element) may include attributes (Attribute)representing attributes of the content corresponding to therepresentation. Attributes that may be configured in representations mayinclude information related to the content (particularly informationrelated to the playback of content) such as codec, bitrate, frame rate,and resolution. Also, the client references the values of theseattributes, and selects the representation.

For example, when there are multiple representations having differentcodecs, bitrates, frame rates, resolutions, and so on for the same videocontent, the client selects the representation corresponding to thecodec, bitrate, frame rate, resolution, and so on that is playable onthe device.

Further, according to the example in the figure, identifiers (id) forthis representation and bitrate (as bandwidth in the figure) aredescribed as attributes, but attributes are not limited to this example.Other attributes such as a MIME type (mimeType) representing playabledata formats, for example, may be included.

Also, a group (group) attribute may be written to the MPDrepresentation. The group represents different components, and thoughrepresentations in the same group cannot be played back simultaneously,representations in different groups can be played back simultaneously.

This will be described with FIG. 17 as a basis. FIG. 17 is a diagramillustrating the related art, in which example MPD data including thegroup attribute is illustrated. According to this example, there arefive representations with id=1 through 5 included in the periodbeginning with “PT0S”.

The group of representations with id=1 through 3 from these fiverepresentations is a group “1”, and the remaining two representationsmake up a group “2”. In this case, neither can the representations withid=1 through 3 belonging to the same group be played simultaneously, norcan the representations with id=4, 5 be played simultaneously.Conversely, the representations in the group “1” and the representationsin the group “2” may be played simultaneously. For example, therepresentation with the id=1 may be played back simultaneously with therepresentation with the id=4 or 5.

Also, according to MPEG DASH (Dynamic Adaptive Streaming over HTTP), anextension is performed to add the representation group(RepresentationGroup) element and a subset (Subset) element to the 3GPPAHS base.

The representation group is an element enabling representationsbelonging to the same group to be organized and described in a highorder of the representations (or in parallel). This will be describedwith FIG. 18 as a basis. FIG. 18 is a diagram illustrating the relatedart, and is an example of MPD data including the representation groupelement.

According to this example, two representation group (elements) beginningwith <RepresentationGroup . . . > and ending with </RepresentationGroup>are included in the period beginning with “PT0S”.

Representations with id=1 through 3 are also included in a firstrepresentation group (representation group “1”). These threerepresentations belong to the same group. Also, representations withid=4, 5 are included in a second representation group (representationgroup “2”). These two representations also belong to the same group.

Conversely, subsets are elements of representations in a high order (orin parallel) representing a set of groups that may be played backsimultaneously. This will be described with FIG. 19 as a basis. FIG. 19is a diagram illustrating the related art, and is an example of MPD dataincluding the subset element.

According to this example, two subset (elements) beginning with <Subset>and ending with </Subset> are included in the period beginning with“PT0S”. Also, described within a first subset is that a group 1 and agroup 2 are included in this subset. Also, described within a secondsubset is that the group 1 and a group 3 are included in this subset.

That is to say, according to the period beginning with “PT0S”, eitherthe first or the second subset may be selected. Also, when the firstsubset is selected, any of the representations from at least eithergroup 1 or 2 are selected. Similarly, when the second subset isselected, any of the representations from at least either group 1 orgroup 3 are selected.

Further, according to this example, three representation group elements“1” through “3” are described. Also, representations with id=1, 2 areincluded in the representation group “1”, representations with id=3, 4are included in the representation group “2”, and a representation withan id=5 is included in the representation group “3”.

That is to say, a subset is first selected from the period beginningwith “PT0S”, and then a representation group corresponding to the groupspecified by the selected subset is selected. Finally, at least onerepresentation included in the selected representation group isselected. For example, when the first subset is selected, at leasteither the representation group “1” or “2” is selected. Also, when bothof these are selected, at least one of the representations with id=1, 2,and at least one of the representations with id=3, 4 are selected.

Here, for example, when a representation of video content is included ingroup 1, a representation of Japanese dialogue content is included ingroup 2, and a representation of English dialogue content is included ingroup 3, the first subset as in FIG. 19 represents a Japanese version ofthe content (video and Japanese dialogue), and the second subsetrepresents an English version of the content (video and Englishdialogue).

That is to say, in this case, content combinations of video and dialogueare restricted by subsets. Also, by selecting a subset, the language ofthe content may be selected. Further, the makeup of the content changeswith the selection of the representations from each group specified bythe selected subset.

In this way, it may be broadly said that subsets supply applicationlevel selections. Also, it may be said that representations supplydevice (device capabilities) level selections, and representation groupsprovide content level selections.

CITATION LIST Patent Literature

PTL 1: Japanese Unexamined Patent Application Publication No.2005-110244 (Apr. 21, 2005)

SUMMARY OF INVENTION Technical Problem

According to the aforementioned related art, all representations,representation groups, and subsets are enclosed within one period, andso information representing continuity of these elements within theperiod is not described.

For this reason, every time a period is changed, it is necessary toparse all representations, representation groups, and subsets includedin the post-transition period, and select subsets and so on, whichcauses a problem in which the processing load is significant whentransitioning between periods.

For example, with the MPD in FIG. 19, it is assumed that the clientselecting and playing the first subset corresponding to the Japaneseversion of the content at the period beginning from “PT0S” will normallycontinue to play the Japanese version of the content during the nextperiod as well (period beginning from “PT30S”).

However, in such a case, it is necessary for the client to again performa selection of subsets, representations and so on after reading andparsing all content for the next period (presentations, representationgroups, and subsets), and so the processing load at the client issignificant.

This is not limited to the case in which the content is selected by therepresentations, representation groups, and subsets as this is also aproblem that occurs with cases in which content is selected afterreferencing the description information describing acquirable content inevery period (playback period).

The present invention is the result of considering the aforementionedproblems with the purpose of providing a playback device or the like inwhich content may easily be selected depending on the content selectedfor a certain playback period when transitioning from a certain playbackperiod to the next playback period to be played.

Solution to Problem

In order to resolve the aforementioned problems, a playback deviceaccording to the present inventions obtains and plays content selectedafter referencing content information on that to be selected includinginformation representing acquirable content in each playback period ofthe content, in which identification information for identifying contentto be played at the playback period to be played next corresponding tothe content selected at a certain playback period is included in theaforementioned content information on that to be selected, and thisplayback device includes selection means configured to select content tobe played at the aforementioned certain playback period afterreferencing the aforementioned content information on that to beselected, and at the same time, for selecting content to be played atthe playback period to be played next in accordance with theaforementioned identification information, acquisition means configuredto acquire the content selected by the aforementioned selection means,and playback means configured to play content acquired by theaforementioned acquisition means at a certain playback period aspreviously described and to continuously play the content to be playedat the playback period to be played next.

Also, in order to resolve the aforementioned problems, a control methodfor the playback device according to the present invention controls theplayback device to obtain and play content selected after referencingcontent information on that to be selected including informationrepresenting acquirable content in each playback period of the content,in which identification information for identifying content to be playedat the playback period to be played next corresponding to the contentselected at a certain playback period is included in the aforementionedcontent information on that to be selected, and this control methodincludes a selection step for selecting content to be played at theaforementioned certain playback period after referencing theaforementioned content information on that to be selected, and at thesame time, for selecting content to be played at the playback period tobe played next in accordance with the aforementioned identificationinformation, an acquisition step for acquiring the content selected bythe aforementioned selection step, and a playback step for playingcontent acquired by the aforementioned acquisition step at a certainplayback period as previously described and for continuously playing thecontent to be played at the playback period to be played next.

Also, in order to resolve the aforementioned problems, a generatingdevice according to the present invention generates content informationon that to be selected including information representing acquirablecontent per playback period, and this generating device includesidentification information generating means configured to generateidentification information for identifying content to be played at theplayback period to be played next, corresponding to content selected ina certain playback period, and generating means configured to generatethe content information on that to be selected including theidentification information generated by the aforementionedidentification information generating means.

Also, in order to resolve the aforementioned problems, a control methodfor the generating device according to the present invention controlsthe generating device to generate content information on that to beselected including information representing acquirable content perplayback period, and this control method includes a step for generatingidentification information for identifying content to be played at theplayback period to be played next, corresponding to content selected ina certain playback period, and a step for generating the contentinformation on that to be selected including the identificationinformation generated by the aforementioned step.

Also, in order to resolve the aforementioned problems, a recordingmedium according to the present invention is a computer-readablerecording medium to which the content information on that to be selectedincluding the information representing acquirable content per playbackperiod is recorded, wherein the aforementioned content information onthat to be selected includes identification information for identifyingthe content to be played at the playback period to be played nextcorresponding to the content selected at a certain playback period, andthe playback device references the aforementioned content information onthat to be selected, selects the content to be played in a certainplayback period, and at the same time, selects the content to be playedat the playback period to be played next in accordance with thepreviously describe identification information.

Also, in order to resolve the aforementioned problems, a data structureaccording to the present invention is a data structure of the contentinformation to be selected including the information representingacquirable content per playback period, and the data structure includesidentification information for identifying content to be played at theplayback period to be played next corresponding to the content selectedat a certain playback period, wherein the playback device references theaforementioned content information on that to be selected, selects thecontent to be played in a certain playback period, and at the same time,selects the content to be played at the playback period to be playednext in accordance with the previously describe identificationinformation.

Advantageous Effects of Invention

As previously described, the playback device according to the presentinventions is configured with selection means configured to selectcontent to be played at a certain playback period after referencing thecontent information on that to be selected, and at the same time, forselecting content to be played at the playback period to be played nextin accordance with the identification information, to identify contentto be played in a playing period which is to be played next, acquisitionmeans configured to acquire the content selected by the aforementionedselection means, and playback means configured to for play contentacquired by the aforementioned acquisition means at a certain playbackperiod as previously described and for continuously playing the contentto be played at the playback period to be played next.

Also, as previously described, the control method of the playback deviceaccording to the present invention is configured with a selection stepfor selecting content to be played at a certain playback period afterreferencing the content information on that to be selected, and at thesame time, for selecting content to be played at the playback period tobe played next in accordance with the identification information, toidentify content to be played in a playing period which is to be playednext, an acquisition step for acquiring the content selected by theaforementioned selection step, and a playback step for playing contentacquired by the aforementioned acquisition step at a certain playbackperiod as previously described and for continuously playing the contentto be played at the playback period to be played next.

Also, as previously described, the generating device according to thepresent invention is configured with identification informationgenerating means configured to generate identification information foridentifying content to be played at the playback period to be playednext, corresponding to content selected in a certain playing period, andgenerating means configured to generate the content information on thatto be selected including the identification information generated by theaforementioned identification information generating means.

Also, as previously described, the control method of the generatingdevice according to the present invention is configured with a step forgenerating identification information for identifying content to beplayed at the playback period to be played next, corresponding tocontent selected in a certain playing period, and a step for generatingthe content information on that to be selected including theidentification information generated by the aforementioned step.

Also, as previously described, the recording medium according to thepresent invention is configured with the content information on that tobe selected includes identification information for identifying thecontent to be played at the playback period to be played nextcorresponding to the content selected at a certain playback period, andthe playback device references the aforementioned content information onthat to be selected, selects the content to be played in a certainplayback period, and at the same time, selects the content to be playedat the playback period to be played next in accordance with theaforementioned identification information.

Also, as previously described, the data structure according to thepresent invention is configured with identification information foridentifying content to be played at the playback period to be playednext corresponding to the content selected at a certain playback period,wherein the playback device references the aforementioned contentinformation on that to be selected, selects the content to be played ina certain playback period, and at the same time, selects the content tobe played at the playback period to be played next in accordance withthe previously describe identification information.

The aforementioned content information on that to be selected includesidentification information identifying the content to be played at theplayback period to be played next corresponding to the content selectedat a certain period. Therefore, by using this content information onthat to be selected, an effect is obtained in which the playback devicemay select the content to be played in a certain playback period, and atthe same time, may readily select the content to be played at theplayback period to be played next in accordance with the aforementionedidentification information.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram illustrating a configuration of client andserver elements included in a content transmission/reception systemrelated to an embodiment of the present invention.

FIG. 2 is a diagram illustrating an example of an MPD including specificinformation on subsets.

FIG. 3 is a flowchart illustrating an example of a processing executedby the client.

FIG. 4 is a diagram describing a method for selecting the subset byusing the subset id during skip playback.

FIG. 5 is a diagram illustrating an example of an MPD including subsetsin which default attributes are described.

FIG. 6 is a diagram illustrating an example of an MPD including aspecialized subset representing a representation group included in allsubsets.

FIG. 7 is a diagram illustrating an example of an MPD includingattributes specifying the next subset.

FIG. 8 is a diagram illustrating an example of an MPD includingattributes specifying the previous subset.

FIG. 9 is a flowchart illustrating an example of a processing executedby the aforementioned client when using an MPD including a nextattribute.

FIG. 10 is a diagram illustrating an example of an MPD including thenext attribute and a previous attribute.

FIG. 11 is a diagram illustrating an example of an MPD including subsetsin which both the next attribute and the previous attribute aredescribed.

FIG. 12 is a diagram describing a method for selecting a subset in aperiod as the skip destination when the period as the skip destinationis not contiguous with the current period.

FIG. 13 is a diagram illustrating an example of an MPD describing thenext attribute only when specifying the id of a subset different fromthe subset id and when there are multiple selections.

FIG. 14 is a diagram illustrating an example of an MPD describing theprevious attribute only when specifying the id of a subset differentfrom the subset id and when there are multiple selections.

FIG. 15 is a diagram describing a priority order of selections in threehierarchies, which are subsets, representation groups, andrepresentations, (a) of the same figure illustrates a case when allthree hierarchies are referenced to perform a selection, (b) of the samefigure illustrates a case when two hierarchies are referenced excludingthe subset hierarchy to perform a selection, and (c) of the same figureillustrates a case when only the representation hierarchy is referencedto perform a selection.

FIG. 16 is a diagram illustrating an example of an MPD according to therelated art.

FIG. 17 is a diagram illustrating the related art, and is a diagramillustrating an example of MPD data including a group attribute.

FIG. 18 is a diagram illustrating the related art, and is a diagramillustrating an example of MPD data including a representation groupelement.

FIG. 19 is a diagram illustrating the related art, and is a diagramillustrating an example of MPD data including a subset element.

FIG. 20 is a diagram illustrating an example of an HTML documentdescribing a URL specifying the subset to be played.

FIG. 21 is a diagram illustrating a relationship between a selected URLand an MPD parsing range specified from this URL.

FIG. 22 is a diagram illustrating a relationship between a URL using anattribute value of the group in the specification for that to be playedand an MPD parsing range specified from this URL.

FIG. 23 is a diagram illustrating a relationship between a URLspecifying that to be played using a language attribute for arepresentation group and an MPD parsing range specified from this URL.

FIG. 24 is a diagram illustrating a relationship between a URLspecifying a period for that to be played by the id of a period and anMPD parsing range specified from this URL.

FIG. 25 is a diagram illustrating a relationship between a URLspecifying a period for that to be played and the subset to be playedand an MPD parsing range specified from this URL.

FIG. 26 is a diagram illustrating that to be parsed as specified fromthe URL description in FIG. 25.

FIG. 27 is a diagram illustrating an example of a playback point of theMPD to be played, and a URL generated when playback is interrupted atthis playback point.

FIG. 28 is a diagram illustrating an example of an MPD referencinganother MPD.

FIG. 29 is a diagram illustrating a reference relationship between aperiod for a drama main story and a period for a digest video when usinga digest video of a drama main story as a selection menu.

FIG. 30 is a diagram illustrating an example of an MPD for actualizing atrick play.

DESCRIPTION OF EMBODIMENTS First Embodiment

Hereafter, a first Embodiment of the present invention will be describedin detail with FIG. 1 through 6 as a basis.

[Overview of System]

First, an overview of a content transmission/reception system accordingto the present embodiment will be described with FIG. 1 as a basis. FIG.1 represents an embodiment of the present invention and is a blockdiagram illustrating a configuration of elements for a client (playbackdevice) 1 and a server (generating device) 2 included in a contenttransmission/reception system 3.

As illustrated, the client 1 is provisioned with a client control unit10 for organizing and controlling operation of the client 1, a clientstorage unit 11 for storing data used by the client 1, and a clientcommunication unit (communication unit) 12 for the client 1 tocommunicate with external devices through a network. The client controlunit 10 also includes a content selection unit (selection means) 13, arequest execution unit (acquisition means) 14, and a content playbackunit (playback means) 15.

The content selection unit 13 acquires description information (contentinformation on that to be selected) of content including informationrepresenting acquirable content for each playback period (period), andselects the content to request from the server 2 according to theacquired description information. Specifically, the content selectionunit 13 receives an MPD as the description information from the server 2(content information on that to be selected), and identifies the subsetto be selected for the next period by referencing the id (identificationinformation) of the subset (group specification information) describedin the MPD. Also, the content to request from the server 2 is selectedfrom the identified subset.

Though details will be described later, the MPD according to the presentembodiment includes identification information for identifying contentto be played during a playback period for the next of that to be playedcorresponding to content selected during a certain playback period. Thecontent selection unit 13 may readily select the content for thepost-transitioned period by referencing this identification information.

The request execution unit 14 transmits a request requesting the contentselected by the content selection unit 13 to the server 2, and soacquires the content from this. Here, the request execution unit 14transmits the request by HTTP. Further, the example here is described inwhich content is acquired from the server 2, but may also be acquiredfrom another server.

The content playback unit 15 plays the content received by the requestfrom the request execution unit 14 in order of periods. Further, theplayed content may be output from displays, speakers, and so onprovisioned to the client 1, and may be output from displays, speakers,and so on connected to the client 1 wirelessly or by a wired connection.

Conversely, the server 2 is provisioned with a server control unit 20for organizing and controlling the operation of the server 2, a serverstorage unit 21 for storing data used by the server 2, and a servercommunication unit 22 for the server 2 to communicate with externaldevices through a network. Also, the server control unit 20 includes adescription information transmitting unit 23 and a response executionunit 24, and the server storage unit 21 stores a content 25 and adescription information (content information on that to be selected) 26.

The description information transmitting unit (identificationinformation generating means, generating means) 23 transmits thedescription information to the client 1. Specifically, the descriptioninformation transmitting unit 23 reads the description information 26stored in the server storage unit 21, and transmits this to the client 1via the server communication unit 22. As previously described, an MPD isused here as the description information.

The response execution unit 24 transmits content to the client 1depending on the request received from the client 1. Specifically, theresponse execution unit 24 reads the content 25 stored in the serverstorage unit 21 when the request is received, and transmits this to theclient 1 via the server communication unit 22.

The content 25 is the content corresponding to the request from theclient 1, and is content such as video data, audio data, character data,and so on, for example.

The description information 26 is information related to the content(here, the content 25 stored in the server storage unit 21) that may beprovided to the client 1 from the server 2. Specifically, thedescription information 26 is an MPD in which the representation(content specification information) representing content which becomes aselection candidate is described in each period, and attributes (codec,bitrate, frame rate, resolution, etc.) of this representation aredescribed in each representation. Details on the MPD will be describedlater.

Further, either or both of the content 25 and the descriptioninformation 26 may be recorded in an external recording mediumdetachably mounted to the server 2, and may be recorded in an externaldevice accessible by the server 2. That is to say, the content 25 andthe description information 26 may be stored in a state acquirable bythe server 2, and there storage destination is not particularly limited.

Also, the content transmission/reception system is configured bymultiple servers 2, and the configuration may include different servers2 for providing the content 25 and the description information 26.

Also, the server 2 or previously described external device may beprovisioned with a content encoding unit configured to encode content,and a description information generating unit configured to generate thedescription information 26. Also, at least either the content 25 or thedescription information 26 may be generated in real time by thisconfiguration. The delivery of the content 25 generated in real time isa so-called live delivery.

Further, according to MPEG DASH MPD, a portion of the contents isdivided as external data, which may be referenced using xlink. For thisreason, when dividing external data for each representation groupbelonging to the period under analysis, once all of the external data isacquired, it becomes necessary to perform a selection processing.

In order to acquire this external data, communication by the HTTPprotocol is used, but communication by the HTTP protocol does notguarantee real time capabilities. For this reason, there is a problem inthat as the amount of external data to be acquired increases, there isincreased risk that streaming playback will be interrupted due tocommunication delay of acquiring external data. According to the presentinvention, this kind of problem may be resolved by using theaforementioned identification information.

[MPD Including Subset Identification Information]

An MPD including subset identification information will be describedwith FIG. 2 as a basis. FIG. 2 is a diagram illustrating an example ofan MPD including subset identification information.

According to the illustrated example, the difference as compared to theMPD according to the related art as in FIG. 19 is that identificationinformation (id) for identifying the subset is added to each subset.This id is added to each subset included in each period, and thisenables the subset to be easily selected depending on the subsetpreviously selected when selecting a subset in another period after asubset has been selected in a certain period.

Specifically, a period beginning from “PT0S” (0 second) and a periodbeginning from “PT30S” (30 second) are described in the MPD in FIG. 2.Three subsets are included in the period beginning from “PT0S”. Thefirst subset has an id of 1 and includes a group 1 (hereafter, group=“1”will be written in this way, and this applies to other groups as well)and a group 2, the second subset has an id of 2 and includes a group 3and a group 4, and the third subset has an id of 3 and includes a group5.

Also, three subsets are included in the period beginning from “PT30S”,the first subset has an id of 1 and includes the group 1, the secondsubset has an id of 2 and includes the group 2, and the third subset hasan id of 3 and includes the group 3.

Further, though not illustrated in the same figure, other than thesubset elements, representation group elements (content affiliationinformation) are included in each period as with the example in FIG. 19.Also, the client 1 selects the representation from the representationgroup depending on the selected subset.

When selecting the representation using this kind of MPD, afterperforming the selection during a certain period, the client 1identifies the subset to be selected by referencing the id of the subsetwhen performing the selection of the next period.

For example, when the subset with an id of 1 during the period beginningwith “PT0S” is selected, the client 1 also selects the subset with an idof 1 for the continuing period beginning with “PT30S”. That is to say,the subsets with the same id value are provisioned with a definition(Semantics) that representing the set that is to be continuouslyselected.

As a result, the client 1 may only analyze the subset having an id of 1to select the content during the period beginning with “PT30S”, and doesnot perform an analysis of all subsets as according to the related art.Therefore, the reselection processing load may be significantly reducedwhen transitioning between periods, as compared to a case when using theMPD according to the related art.

That is to say, when using the MPD according to the related art, theinformation of the subsets, representation groups, and representationsselected at the previous “PT0S” are referenced during the periodbeginning from “PT30S”, as illustrated. Also, using the referenceinformation, the subsets, representation groups, and representationsmust be reselected on the basis of the information of all subsets,representation groups, and representations, of “PT30S” again. For thisreason, the processing load on the client 1 has been significant.

Conversely, when using the MPD as in FIG. 2, the client 1 may performthe selection after referencing only the representation groups andrepresentations included in the subset of the same id as the subsetselected for the previous period.

In this way, by refining the information to be referenced, theprocessing load on the client 1 is reduced. Also, by adding the same idto the subsets that are desired to be continuously selected, thecontinuity (continuity intended by the creator of the MPD) of contentmay be reliably maintained when transitioning between periods.

Further, the processing to reference the id of the selected subset andselecting the subset for the next period is applicable to playback inwhich the advancement of time is reversed such as for fast rewind. Forexample, when performing playback in an order to return from the periodbeginning with “PT30S” to the period beginning with “PT0S”, the subsetwith the same id as the subset selected at the period beginning with“PT30S” may be selected at the period starting with “PT0S”.

Also, the groups included in the subset with the same id do not have tomatch regarding each period. Also, the subsets to be continuouslyselected may be subsets desired to be continuously selected on thecontent providing side such as the server 2 or the side of the creatorof the MPD.

For example, when handling video content, a shared id may be added tosubsets corresponding to the Japanese dialogue (subsets specifying videogroups and Japanese dialogue groups). Also, a different shared id may beadded to subsets corresponding to the English dialogue (subsetsspecifying video groups and English dialogue groups).

As a result, when subsets corresponding to the Japanese dialogue areinitially selected, the subsets selected afterwards may be restricted tothe subsets with the same id, and the Japanese dialogue is maintainedeven as the period is changed. The case when initially selecting theEnglish dialogue is similar. In this way, by specifying the subsets, thecontent is specified at the application level.

Also for example, advertising (CM) content matching the content selectedby the user may be inserted between the periods representing the videocontent as different periods. In this case, by designating the id of thesubset used by the video content and the id of the subsets of theadvertising content to the same value, the continuity of content may bemaintained as intended by the content provider.

[Processing Flow]

Next, the processing flow executed by the client 1 will be describedwith FIG. 3 as a basis. FIG. 3 is a flowchart illustrating an example ofa processing executed by the client 1.

The content selection unit 13 of the client 1 receives the MPD via theclient communication unit 12 (S1). This MPD acquires the descriptioninformation 26 stored in the server storage unit 21 by the descriptioninformation transmitting unit 23 in the server 2 as the MPD, and istransmitted to the client 1 via the server communication unit 22 (thismay also be a multicast transmission to multiple clients including theclient 1).

Further, the method in which the server 2 acquires the MPD is notlimited thusly, for example, the MPD recorded in a recording mediumexternal to the server 2 may be acquired, and the MPD may be acquiredfrom another device that generates or stores the MPD. Also, thedescription information transmitting unit 23 may generate the MPD.Generation of the MPD will be described later.

Next, the content selection unit 13 performs the reading and analysis ofthe first period (Period#1) in the received MPD (S2). Also, theselection and setting of the subset is performed on the basis of theanalyzed MPD (S3). Here, the subset with an id=k is selected. Further,the selection of the subset is performed according to user operation, oris automatically performed by the processing of the content selectionunit 13 without user operation.

When in accordance with user operation, the content selection unit 13may perform processing such as display of an image to enable theselection of the subset. Also, when automatically selected, this isselected according to predetermined criteria and on the basis of theanalysis result of S2. For example, the subset with the smallest idvalue may be selected, of the subset with a previously specified id maybe selected.

Next, the content selection unit 13 selects the representation groupcorresponding to the group specified by the subset with the id=k fromthe Period#n from the MPD received at S1 (S4). According to theprocessing of the first S4 after the flow has started, therepresentation group for Period#1 read at S2 is selected. That is tosay, n=1.

Further, as in the case when multiple representation groups arespecified for the subset, and only a portion of the specified group isselectable (when all groups specified for the subset do not need to beselected), for example, when there are selections regarding theselection of the representation group, similar to the selection of thesubset at S3, this may be selected by the user, or may be automaticallyselected.

Next, the content selection unit 13 selects the representation from therepresentation group selected at S4. The selection of the representationis also similar to the selection at S3 and S4, may be selected by theuser, or may be automatically selected.

The content selection unit 13 notifies the request execution unit 14 ofthe selected representation as the content to be played is determined bythe selection of the representation. The request execution unit 14 whichhas received this notification generates the request corresponding tothe representation that has been notified. Also, the delivery of thedata (content corresponding to the representation) for therepresentation selected by the content selection unit 13 is requested tothe server 2 by transmitting this to the server 2 via the clientcommunication unit 12.

The response execution unit 24 in the server 2 receives this request,reads the requested data (content) from the server storage unit 21, andtransmits this to the client 1 via the server communication unit 22.Further, the content to be transmitted may be acquired from the serverstorage unit 21, or may be acquired from another recording medium oranother device. Also, by instructing another device, this may betransmitted to the client 1 from this device.

The content playback unit 15 in the client 1 receives the data (content)requested by the request execution unit 14 via the client communicationunit 12, and generates this according to the order of the periods (S6).

Further, the order of the periods is the order of the periods withsmaller times as specified by “PT(time) when performing playback in theordered direction, and is the order of the periods with larger timeswhen performing playback in the reverse direction. Also, the playback inthe ordered direction is playback in the direction of the advancement oftime, and corresponds to normal playback, fast forward playback, and soon. Conversely, playback in the reverse direction is playback in thedirection as a returning of time, and corresponds to fast rewindplayback and so on.

Here, the content selection unit 13 confirms whether or not the subsethas changed after the representation selected at S5 is notified to therequest execution unit 14 (S7). Here, the changed subset is designatedwith an id=k′. The changing of the subset may be performed according touser operation, or may be performed automatically.

Also, when it has been confirmed that the subset changed (YES at S7),the processing returns to S4 and the content selection unit 13 selectsthe representation group from the changed subset, that is to say, thesubset with the id=k′.

Conversely, when it has not been confirmed that the subset has changed(NO at S7), the content selection unit 13 confirms whether or not thecontent playback unit 15 has finished playback of the content ofPeriod#n (S8).

Here, if playback is not finished (NO at (S8)), the processing returnsto S6, and the content playback unit 15 continues playback of thecontent of Period#n. Conversely, when the playback of the content ofPeriod#n is finished (YES at S8), the content selection unit 13 confirmswhether or not the content playback unit 15 will finish the playback ofcontent (S9). Further, at S9, when the playback of the content for allperiods included in the MPD received at S1 is finished, for example, orwhen there is user operation to finish the playback of the content, thismay be determined as finishing the playback of content.

When it has been confirmed at S9 that playback of content is finishing(YES at S9), the content selection unit 13 finishes the processing.Conversely, when it has been confirmed that the playback of content isnot finishing (NO at S9), the processing returns to S4, and the contentselection unit 13 selects the representation group for the subset withthe id=k from the next period after Period#n, that is to say, Period#n+1(S4).

As previously described, the content selection unit 13 automaticallyselects the subset with an id selected at the previous period at thenext period. Therefore, when selecting the subset during a break inperiods, subsets other than those with the id selected at the previousperiod may be removed from that which is to be analyzed. For thisreason, the processing load on the client 1 is lighter as compared tocase when using the MPD according to the related art, which requires allsubsets to be analyzed.

Further, according to the aforementioned example, a selection has beenperformed for the content of the next period at the S4 through S6 afterit was confirmed that the playback finishes at S8, but the timing ofthis selection is not limited to this example, and may be any timingafter the processing of S5. Also, the timing to perform the request andreception of the content after the selection may be before the playbackof the previous period finishes. The performance of a smooth playback ata break in periods is enabled by performing the selection and request ofthe next period before the playback of the previous period finishes.

[Skip Playback]

Other than the transition to the next period after the playback of oneperiod finishes, the subset id may also be used during skip playback inwhich there is a transition to another period before the playback of oneperiod finishes. This will be described with FIG. 4 as a basis.

FIG. 4 is a diagram describing a method for selecting a subset using thesubset id during skip playback. According to the illustrated example,the subset with an id=1 is selected during the period beginning with“PT0S”, and a skip from this period to a period beginning with“PT02M00S” is performed.

The client 1 selects the subset with the same id as the id selectedduring the previous playback period even when transitioning betweenperiods due to this kind of skip playback. That is to say, asillustrated, the subset with the id=1 is also selected during the periodbeginning with “PT02M00S”.

Therefore, the processing load on the client 1 during skip playback issignificantly reduced as compared to an example of the related art inwhich all subsets included in the period as the skip destination had tobe analyzed. Further, other than skip playback, the selection of thesubset may be similarly performed using the id for playback such as highspeed playback (fast forward), fast rewind, and a summary playback inwhich an order of only the initial portion of each period is playedwhile skipping.

[Attributes Specifying the Specified Subset]

A configuration may be implemented in which information representing thespecified subset is written into the subset attributes for the purposeof readily selecting the subset for the playback start period. This willbe described with FIG. 5 as a basis. FIG. 5 is a diagram illustrating anexample of an MPD including subsets to which default attributes, whichis information representing the specified subset, is written.

The default=“true” and default=“false” in the same figure are thedefault attributes (substitute specification information), and thesubsets to which the default=“true” is added are the specified subsets.Also, the subsets to which the default=“false” is added are the subsetswhich are not specified.

As illustrated in period#3 in the same figure, the default=“true” may beadded to multiple subsets included in one period. In this case, whenselecting the specified subset, one subset is selected from the subsetsto which the default=“true” is added. Further, according to the examplein the same figure, the default=“false” is added to all subsets to whichthe default=“true” is not added, but the addition of the default=“false”may be omitted.

When there is no specification of the playback start subset externallyfrom user operation, etc., the selection of the appropriate subset andthe starting of playback are enabled without performing analysis onother subsets by having these default attributes written. That is tosay, when the subset is not specified, the client 1 selects the subsetsto which the default=“true” is added.

Also, when transitioning periods and there are no ids for the subsetsselected at the previous period, a configuration may be implemented inwhich specified subsets to which the default=“true” are added aretemporarily selected at the current period, and subsets with theaforementioned id are selected at the next period.

Regarding the example in FIG. 5, for example, when the client 1 selectsthe subset with an id=3 at the period#1 and starts playback, as thereare no subsets with the id=3 in period#2, the specified subset with anid=1 is substituted, and playback continues. Also, at the period#3,there are subsets with the id=3, and so playback continues with thereselection of the subset with the id=3.

By implementing such a configuration, even when subsets with the same idare not included in all periods, the selected subsets are able to have aconstant continuity.

For example, let us assume a case in which period#1 and #3 are videocontent, period#2 is advertising content, and each subset representsselections for dialogue data (id=1: Japanese, id=2: English, and id=3:French). In this case, even if the dialogue data corresponding to alllanguages has not been prepared for the advertising content to match thevideo content, the dialogue data for the video content may still bedesignated with the same language. For example, when the user selectsthe French dialogue data at the period#1, the advertising content atperiod#2 has Japanese dialogue, but when returning to the video contentat period#3, the playback is performed using the French dialogue data.

[Handling of Representation Groups Included in all Subsets]

Here, there is a rule regarding subsets in MPEG DASH in whichrepresentation groups that are not included in any subset are to beincluded in all subsets. Therefore, when extracting only representationgroups clearly specified by subsets, there is no guarantee that allrepresentation groups included in these subsets will be extracted.

For this reason, in order to reliably extract all representation groupsincludes in subsets, all subsets had to be referenced to confirm whetheror not there have been representation groups not included in any of thesubsets.

In order to avoid such a cumbersome processing, when representationgroups are included in all subsets in the MPD, it is preferable toclearly write their existence. For example, a special subset may bedefined to represent representation groups included in all subsets. Thiswill be described with FIG. 6 as a basis.

FIG. 6 is a diagram illustrating an example of an MPD including aspecial subset representing representation groups included in allsubsets. According to the illustrated MPD, a subset with an id=0 (groupspecification information for essential selection) is added. This subsetis a special subset representing representation groups included in allsubsets.

That is to say, when the client 1 confirms that the subset with the id=0is included in the MPD, representation groups included in this subsethave to be selected for any period. Further, the client 1 does notselect only the subset with the id=0.

Therefore, when the subset with the id=1 is selected at the periodbeginning with “PT0S” as in the example in FIG. 6, the client 1 selectsboth the subset with the id=1 and the subset with the id=0 at thecontinuing period beginning with “PT30S”.

In this way, by defining the subset with the id=0, the client 1 onlyanalyzes the subsets with the same id as subsets before transitioningand the Subset with the id=0 when transitioning between periods, and soall representation groups included in subsets may be reliably extracted.

Further, other than defining a special subset, a restriction may beimplemented in which representation groups included in subsets have tobe clearly defined. As a result, by analyzing only the subsets with thesame id as the subsets selected at the previous period, allrepresentation groups included in subsets may be reliably extracted.

Second Embodiment

Next, a second Embodiment of the present invention will be describedwith FIG. 7 through 15 as a basis. According to the first Embodiment,examples have been illustrated in which subsets with the same id as thatwith ids previously selected are selected at the next period, butaccording to the present embodiment, examples are illustrated in whichattributes representing continuity between subsets are further added. Inaddition to the subsets with the same id, the selection of optionalsubsets specified by these attributes when crossing periods is enabledby adding these attributes. Further, the configuration of the system andthe devices (refer to FIG. 1) are the same as that for the firstEmbodiment.

[Attributes Specifying Subsets to be Selected at the Next Period]

First, attributes specifying subsets to be selected at the next periodwill be described with FIG. 7 as a basis. FIG. 7 is a diagramillustrating an example of an MPD including attributes specifyingsubsets to be selected at the next period.

According to the illustrated MPD, similar to the aforementionedembodiment, an id is written for each subset. Also, other than the id, a“next=” “ ” is written in the subset in the period beginning from“PT0S”. This is an attribute specifying the subset to be selected at thenext subset. Further, hereafter, this attribute will be referred to as anext attribute.

The next attribute is specified in which the subset to be selected atthe period immediately after the period already selected (in theplayback time order) is given an id with a format of “(id value)”. Whenthe next attribute is included in the subset selected in a certainperiod, the client 1 selects the subset with the id specified by thenext attribute during the period immediately after.

For example, regarding the MPD in FIG. 7, when the subset with the id=1is selected at the period beginning with “PT0S”, the subset with theid=1 is specified by the next attribute included in this subset. Forthis reason, the client 1 selects the subset with the id=1 during theperiod continuing from “PT0S” that begins with “PT30S”.

Also, multiple subsets may be specified by the next attribute. Whenmultiple subsets are specified, the client 1 selects one subset from thespecified subsets. In this case, the range of that to be analyzed in theMPD by the client 1 becomes larger than the case in which only onesubset is specified, but this allows some margin in the selection ofsubsets by the client 1 or the user.

For example, two numbers, 1 and 2, are written for the next attribute inthe subset with the id=2 included in the period beginning from “PT0S” inthe MPD in FIG. 7. This represents that the subset with the id=1 and thesubset with the id=2 are selection candidates during the next period.Therefore, when this subset is selected at the period beginning with“PT0S”, the client 1 selects the subset with the id=1 or id=2 at theperiod beginning with “PT30S”.

Also, subsets with ids different from the subsets including thisattribute may be specified with the next attribute. When the idspecified by the next attribute included in this subset and the id ofthe subset selected at a certain period are different, the client 1selects the id specified by the next attribute during the periodimmediately after.

For example, a subset with an id=4 is specified by the next attribute inthe subset with the id=3 included in the period beginning from “PT0S” inthe MPD in FIG. 7. Therefore, when this subset is selected at the periodbeginning from “PT0S”, the client 1 selects the subset with the id=4.

Further, regarding the last period included in the MPD, as there are noperiods continuing afterwards, the next attribute cannot be written, butthe next attribute can be written in all other periods. For example,regarding the example in FIG. 7, when there are periods continuing afterthe period beginning from “PT30S”, the next attribute may be written forthe period beginning from “PT30S”.

[Attributes Specifying Subsets Selected at the Previous Period]

Next, attributes specifying subsets selected at the previous period willbe described with FIG. 8 as a basis. FIG. 8 is a diagram illustrating anexample of an MPD including the attributes specifying subsets selectedat the previous period.

According to the illustrated MPD, similar to the aforementionedembodiment, an id is written for each subset. Also, other than the id, a“prev=” “ ” is written in the subset in the period beginning from“PT30S”. This is an attribute specifying the subset to be selected atthe previous subset. Further, hereafter, this attribute will be referredto as a previous attribute.

The previous attribute is specified in which the subset selected at theperiod immediately before in the playback time order is given an id witha format of “(id value)”. When the previous attribute is included in thesubset selected in a certain period, the client 1 selects the subsetwith the id specified by the previous attribute during the periodimmediately before.

For example, regarding the MPD in FIG. 8, when the subset with the id=1is selected at the period beginning from “PT0S”, the client 1 referencesthe tag portion of each subset included in the period continuing from“PT0S” that begins from “PT30S”, and confirms the id specified by theprevious attribute. Also, here, the subset with the id=1 is selected atthe period immediately before, and so the subset with the id=1 specifiedin the subset with the id=1 by the previous attribute is selected.

Further, when using only the previous attribute, regarding playback inthe ordered direction, the tag portion of each subset of the next periodhas to be referenced in this way, and so the processing load issignificant as compared to the case in which only the next attribute isused. The case in which playback is performed in the reverse directionusing only the next attribute is similar.

In contrast, when performing playback in the reverse direction, subsetsmay be readily selected by the previous attribute. Similarly, when usingonly the next attribute, the selection of subsets during playback in theordered direction is simple. Therefore, by combining the next attributeand the previous attribute, the advantages of both may be exploited, andthe disadvantages of both may be compensated for. This will be describedlater.

Also, multiple subsets may be specified by the previous attribute. Whenmultiple subsets are specified, the client 1 selects one subset from thespecified subsets during playback in the reverse direction. Also, the idof subsets selected at the previous period during playback in theordered direction selects the subset written to the previous attributeincluded in the specified candidates.

For example, two numbers, 1 and 2, are written for the previousattribute in the subset with the id=1 included in the period beginningfrom “PT30S” in the MPD in FIG. 8. This represents that either thesubset with the id=1 or the subset with the id=2 has to be selectedduring the previous period.

Therefore, when either the subset with the id=1 or the subset with theid=2 is selected at the period beginning with “PT0S”, the client 1selects the subset with the id=1 at the period beginning from “PT30S”during playback in the ordered direction. Also, for playback in thereverse direction, when this subset is selected at the period startingfrom “PT30S”, the subset with the id=1 or id=2 is selected at the periodbeginning from “PT0S”.

Also, subsets with ids different from the subsets including thisattribute may be specified with the previous attribute. When the idspecified by the previous attribute included in this subset and the idof the subset selected at a certain period are different, the client 1selects the id specified by the previous attribute during the periodimmediately before.

For example, a subset with an id=3 is specified by the previousattribute in the subset with the id=4 included in the period beginningfrom “PT30S” in the MPD in FIG. 8. Therefore, when the subset with theid=3 is selected at the period beginning from “PT0S”, the client 1selects the subset with the id=4 at the period beginning from “PT30S”for playback in the ordered direction. Also, for playback in the reversedirection, when this subset is selected at the period beginning from“PT30S”, the subset with the id=3 is selected at the period beginningfrom “PT0S”.

Further, regarding the first period included in the MPD, as there are noprevious periods, the previous attribute cannot be written, but theprevious attribute may be written in all other periods.

[Processing Flow]

Next, the processing flow executed by the client 1 will be describedwith FIG. 9 as a basis. FIG. 9 is a flowchart illustrating an example ofa processing executed by the client 1, in a case of using an MPDincluding a next attribute. Further, here, the processing flow isdescribed when playback in the ordered direction is performed. Also, theprocessing from S11 to S19 in FIG. 9 is similar to the processing fromS1 to S9 in FIG. 3, and so their description is omitted here.

When it has been confirmed that playback of content is finishing at S19(YES at S19), the content selection unit 13 finishes processing.Conversely, when it is confirmed that playback of content is notfinishing (NO at S19), processing proceeds to S20.

As S20, the content selection unit 13 switches the id of the subsetselected at the next period after the Period#n, that is to say, thePeriod#n+1 from the current k to the k′ specified by the next attribute,and processing returns to S14. At S14, the representation groupspecified by the subset with the id=k′ is selected during thePeriod#n+1.

Further, the processing when performing playback in the reversedirection using the MPD including the previous attribute is similar tothe example in FIG. 9. In this case, at S20, the id of the subsetselected at the period to be selected as the next subset (Period#n−1) isswitched to the k′ specified by the previous attribute, and processingreturns to S14.

Conversely, when performing playback in the reverse direction using theMPD including the next attribute, in S20, the content selection unit 13references the value of the next attribute for each subset included inthe period to be selected as the next subset (Period#n−1). Also, thatincluding the next attribute specified in the subsets selected in thecurrent period (Period#n) from the subsets which have been referenced isselected.

Further, when multiple subsets have become candidates, the user may beallowed to select, or the content selection unit 13 may make theselection in accordance with predetermined conditions and similar. Theprocessing when performing playback in the ordered direction using theMPD including the previous attribute is similar.

[Combining the Next Attribute and the Previous Attribute]

As previously described, it is preferable to coming the next attributeand the previous attribute. Here, an example of combining the nextattribute and the previous attribute will be described with FIG. 10 andFIG. 11 as a basis.

FIG. 10 is a diagram illustrating an example of an MPD including thenext attribute and the previous attribute. According the illustratedexample, the next attribute is written in the subsets with ids=1 through3 included in the period beginning from “PT0S”, and the previousattribute is written in the subsets with ids=1 and 2 included in theperiod beginning from “PT30S”.

In this way, when using the MPD combining the next attribute and theprevious attribute, the client 1 may readily select the subset for theperiod after transitioning by referencing the next attribute duringplayback in the ordered direction. Also, for playback in the reversedirection, the subset may be readily selected for the period aftertransitioning by referencing the previous attribute.

Therefore, whether transitioning between period during playback in theordered direction, or transitioning between periods during playback inthe reverse direction, the processing load on the client 1 is lessened.For this reason, fast forward, fast rewind, high-speed skip playback inthe ordered direction or the reverse direction may be performedefficiently and smoothly.

Further, when writing such an MPD, it is preferable that the subsetsspecified by the next attribute and the previous attribute do notcontradict each other. A skip playback method for a case of using thenext attribute and the previous attribute will be described later.

Here, the example in FIG. 10 illustrates that either the next attributeor the previous attribute is written to one subset, but regarding an MPDincluding more at least three periods, both the next attribute and theprevious attribute may be written to one subset.

FIG. 11 is a diagram illustrating an example of an MPD including subsetsto which both the next attribute and the previous attribute are written.According to the illustrated example, the next attribute is written tothe subsets with ids=1 to 3 included in the period beginning from“PT0S”. Also, both the previous attribute and the next attribute arewritten to the subsets with ids=1, 2, and 4 included in the periodbeginning from “PT30S” and to subsets with ids=1, 2, and 4 in the periodbeginning from PT01M00S”.

When using such an MPD, the client 1 references the next attributeduring playback in the ordered direction, and selects the subset duringthe period immediately after. For example, when performing playback inthe ordered direction, and the subset with the id=1 is selected at theperiod beginning from “PT0S”, the subset is selected for each periodaccording to the next attribute as illustrated. Conversely, for playbackin the reverse direction, the previous attribute is referenced, and thesubset is selected for the period immediately before.

For example, when the subset with the id=1 is selected at the periodbeginning from “PT30S”, the client 1 references the next attribute inthe subset and selects the identified subset with the id=1 whentransitioning between periods during the performance of playback in theordered direction. Conversely, when performing playback in the reversedirection, the previous attribute is reference in this subset, and theidentified subset with the id=1 is selected when transitioning betweenperiods.

[Skip Playback]

When performing skip playback, the periods as skip destinations are notlimited to those neighboring the current period on a timeline. Accordingto the example described for the first Embodiment in which the subsetswith the same id are selected, subsets with the same id are selectedeven if the period as the skip destination does not neighbor the currentperiod on a timeline. However, the processing of the case when using thenext attribute or the previous attribute according to the presentembodiment is different. Here, the processing in the case when theperiod as the skip destination does not neighbor the current period willbe described with FIG. 12 as a basis.

FIG. 12 is a diagram describing a method for selecting subsets for theperiod as the skip destination when the period as the skip destinationdoes not neighbor the current period. Further, the MPD written in thefigure is the same as the MPD in FIG. 11.

When performing a skipping to periods that do not neighbor the currentperiod, that is to say, periods that are not immediately before orimmediately after the current period, the subset to be selected isidentified for the period as the skip destination by the following theorder of the values of the next attribute or the previous attribute.This is because the next attribute is that specifying the subset to beselected at the period immediately after regarding playback time, andthe previous attribute is that specifying the subset to be selected atthe period immediately before regarding playback time.

For example, with the example in FIG. 12, let us assume a case in whichafter the subset with the id=1 is selected at the period beginning from“PT0S”, playback is skipped to the period beginning from “PT01M00S”until the playback for the period beginning from “PT0S” finishes.

In this case, the client 1 identifies from the next attribute includedin the subset with the id=1 selected for the period beginning from“PT0S” that the subset to be selected at the period immediately afterthis period (period beginning from “PT30S”) is the subset with the id=1.

Also, it is identified from the next attribute included in the subsetwith the id=1 for the period beginning from “PT30S” that the subset tobe selected at the period immediately after this period (periodbeginning from “PT01M00S”) is the subset with the id=1. As a result, itmay be identified that the subset with the id=1 should be selected atthe period beginning from “PT01M00S”, which is the skip destination.

Skipping in the reverse direction is similar in that the subset to beselected for the period as the skip destination may be identified byfollowing the values of the ids specified by the previous attribute fromthe period as the skip origination to the period as the skipdestination.

[Example of Writing the Next Attribute or the Previous Attribute Only inNecessary Portions]

According to the aforementioned examples, the examples illustrated thatthe next attribute or the previous attribute are written even whenspecifying subsets with the same id as the id of the subset. However,the next attribute and the previous attribute may only be used whenspecifying subsets with ids that are different from the id of the subsetor when there are multiple selections.

As a result, the subset to be specified may be changed by a simpleprocessing in which the next attribute or the previous attribute areadded to portions where it is desired to change the specification. Thiswill be described with FIG. 13 and FIG. 14 as a basis.

FIG. 13 is a diagram illustrating an example of an MPD to which the nextattribute is only written when specifying subsets with ids differentfrom the id of the subset, and when there are multiple selections.According to the illustrated example, the subsets with ids=1 through 3are included in the period beginning from “PT0S”. The next attribute isnot written to the subset with the id=1 from this group. In contrast,the next attribute specifying the subset with the id=1 or id=2 iswritten to the subset with the id=2, and the next attribute specifyingthe subset with the id=4 is written to the subset with the id=3.

In this way, when using an MPD including subsets to which the nextattribute is written and subsets to which they are not written, adefinition is provisioned (Semantics) in which the subsets with the sameid are continuously selected, and this becomes the default.

Therefore, when using the MPD in FIG. 13, the client 1 selects thesubset with the same id (id=1) at the next period in accordance with thedefaults when the subset with the id=1 is selected at the periodbeginning from “PT0S”. Further, the next period may be the periodimmediately after (period beginning from “PT30S”), or may be a periodthat does not neighbor on a timeline (during skip playback, forexample).

Also, when the subset with the id=2 is selected for the period beginningfrom “PT0S”, the subset with the id=1 or the id=2 is selected at theperiod immediately after (period beginning from “PT30S”) in accordancewith the next attribute written in this subset.

Also, when the subset with the id=3 is selected for the period beginningfrom “PT0S”, the subset with the id=4 is selected at the next period(period beginning from “PT30S”) in accordance with the next attributewritten in this subset.

Conversely, FIG. 14 is a diagram illustrating an example of an MPD inwhich the previous attribute is written only when specifying subset withids different from the id of the subset, and when there are multipleselections. According to the illustrated example, the subsets withids=1, 2, and 4 are included in the period beginning from “PT30S”. Theprevious attribute is not written into the subset with the id=2 fromthis group. In contrast, the previous attribute specifying the subsetswith the id=1 or id=2 is written into the subset with the id=1, and theprevious attribute specifying the subset with the id=3 is written intothe subset with the id=4. When using such an MPD, the continuousselection of subsets with the same id values becomes the default.

Therefore, when performing playback in the reverse direction using theMPD in FIG. 14, the client 1 selects the subset with the same id (id=2)at the next period (period beginning from “PT0S”) in accordance with thedefaults when the subset with the id=2 is selected for the periodbeginning from “PT30S”.

Also, when the subset with the id=1 is selected for the period beginningfrom “PT30S”, the subset with the id=1 or id=2 is selected at the nextperiod (period beginning from “PT0S”) in accordance with the previousattribute written in this subset.

Also, when the subset with the id=4 is selected for the period beginningfrom “PT30S”, the subset with the id=3 is selected for the next period(period beginning from “PT0S”) in accordance with the previous attributewritten in this subset.

Third Embodiment

According the aforementioned embodiments, examples have been describedin which the selection of subsets when transitioning between periods issimple by adding the id attribute to the subset, or adding the nextattribute or the previous attribute, and referencing the values of suchattributes. According to the present embodiment, examples will bedescribed in which the selection of representation groups andrepresentations is simple by similar attributes. Further, theconfiguration of the system and devices (refer to FIG. 1) is the same ofthat for the first Embodiment.

[Example Using the Id According to the Related Art]

With the MPD according to the related art, the id attribute may bewritten into the representation group. Therefore, the representationgroup to be selected may also be identified at the period aftertransitioning by referencing the id of the representation group in theway the subset to be selected at the period after transitioning isidentified by referencing the id of the subset regarding theaforementioned embodiments.

That is to say, the client 1 may select the representation group withthe same id as the representation group selected for a certain period atthe next period.

For example, when performing a selection of content using the MPDaccording to the related art as in FIG. 18, the client 1 may select therepresentation group with “1” for the next period when therepresentation group with “1” has been selected for the period beginningfrom “PT30S”.

Also for example, when the representation group with “1” and “2” isselected for the period beginning from “PT30S”, the client 1 may selectthe representation group with “1 and “2” for the next period. Further,as ultimately at least one content may be selected, when selectingmultiple representation groups in this way, it does not matter if acontent is not selected from the group of selected representationgroups.

As a result, the client 1 may readily select the representation group tobe selected when transitioning between periods, and at the same time,maintain continuity at the content level. However, regarding content tobe played continuously, the representation groups included in thiscontent have to share the same id.

Similarly, with the MPD according to the related art, the id attributemay be written into the representation, and so the representation to beselected may also be identified at the period after transitioning byreferencing the id of the representation.

That is to say, the client 1 may select the representation with the sameid as the representation selected for a certain period at the nextperiod.

As a result, the processing load on the client 1 from selectingrepresentations may be reduced, and at the same time, continuity at thedevice (device performance) level may be maintained. For example,regarding content at the same device level (bit rate, resolution, etc.),the ids of the representations corresponding to this content have to beshared. As a result, the client 1 identifies the content to be selectedwhen transitioning between periods by only referencing the ids ofrepresentations, and may readily select the content at the same devicelevel after transitioning periods.

However, according to the related art, there is no restriction to writethe same id for the same content (content to be continuously played) atthe representation group level or the representation level. Also, whenadvertising or other content has been inserted into a certain content,as the creator that wrote the id is different for each content, it iseven less likely that the same id is written for the same content(content to be continuously played).

For this reason, even if a representation group id or a representationid is written in the MPD according to the related art, most cases ofreferencing such ids when transitioning between periods had no effect onthe selection of suitable content.

That is to say, the id for the representation group and therepresentation in the MPD according to the related art may not be saidto represent continuity of representation groups and representationswhen transitioning between periods.

In contrast, the MPD described here is created under a restriction inwhich the same id is added to representation groups to be selectedcontinuously, and the same id is added to representations to be playedcontinuously. According to such an MPD, the id for the representationand representation group functions as information representingcontinuity for representations and representation groups whentransitioning between periods.

For example, let us assume a case in which it is desirable to have theserver 2 insert advertising content into one content made up of multipleperiods (referred to as content A) to be played by the client 1. In sucha case, the server 2 may generate an MPD in which the same id as the idof the representation groups in the content A is written for therepresentation groups of the advertising content for the period in whichit is desired to insert the advertising content, and transmit this tothe client 1. As a result, may cause the client 1 to play the content Awith the advertising content inserted in a desired period.

Further, when using multiple MPDs created under the restriction in whichthe same id is added to content to be played continuously, therepresentation group with the same as id as the id selected at theperiod of the MPD before being changed may be selected when playbackcontinues after switching to another MPD during playback based on acertain MPD. This is similar for subsets and representations as well.

[Example of Adding New Information]

The processing load on the client 1 may be reduced, and at the sametime, continuity of representation groups and representation may bemaintained when transitioning between periods also by newly addinginformation representing representation groups or representations to beselected at the next period into the MPD.

For example, identification information for identifying representationgroups to be selected at the next period may be written as an attributethat is different from the representation group id. Also, thisidentification information may be that which specifies the id of therepresentation group to be selected at the next period.

Also, this identification information may be that which specifies therepresentation group to be selected for optional periods includingperiods not continuing on a timeline, which is that other thanimmediately before or immediately after the current period, as that tobe played next. Also, as with the next attribute and the previousattribute, this may specify the representation group to be selected forthe period immediately after or immediately before.

When performing a selection using an MPD including such identificationinformation, the client 1 reads out the identification information fromthe attributes of the representation group selected at the currentperiod. Also, the representation group identified by the identificationinformation readout is selected for the period after transitioning.

This is also similar for representations in that identificationinformation for identifying the representation to be selected at thenext period may be written as an attribute, in addition to therepresentation id.

When performing a selection using an MPD including such identificationinformation, the client 1 reads out the identification information fromthe attributes of the representation selected at the current period.Also, the representation identified by the identification informationreadout is selected for the period after transitioning.

[Order of Priority]

As previously described, other than subsets, representation groups andrepresentations may also be specified as that which is to be selected atthe period after transitioning. Also, these specifications may becombined. That is to say, at least two of the subsets, representationgroups, and the representations may be specified.

Here, after the subset is determined, the representation groups whichmay be selected become limited, and so this may be said to be a layerabove the representation group. Also, the representation group includesthe representations, and so it may be said that this layer is also abovethe representations.

When performing a specification of multiple layers having such verticalrelationships, it is desirable to previously set an order of priority sothat no contradictions develop in selections at each layer. Here, theorder of priority for selections at each layer will be described withFIG. 15 as a basis.

FIG. 15 is a diagram describing the order of priority for selections atthree layers, which are the subsets, the representation groups, and therepresentations, and (a) of the same figure illustrates when referencingall three layers, (b) of the same figure illustrates when referencingtwo layers without the subset layer, and (c) of the same illustrateswhen referencing only the representation layer. Further, the subsets arelabeled as Subset, the representation groups are labeled as RepGrp, andthe representations are labeled as Rep in FIG. 15.

When referencing the selections for all three layers for the periodbefore transitioning and performing a selection for the period aftertransitioning, the order of priority is in an order fromsubsets>representation groups>representations. Specifically, asillustrated in (a) of the same figure, the client 1 first selects thesubset with the same id as the subset selected at the period (period#n)before transitioning (or another subset specified in this subset) forthe next subset (period#n+1) as well.

Next, the client 1 selects the representation with the same id as therepresentation selected at the period before transitioning (or anotherrepresentation specified in this representation). However, when therepresentation selected at the period before transitioning is notincluded in the previously selected subset, another representation thatis included in this subset is selected.

That is to say, the subset for the next period is selected in accordancewith the id of the subset selected at the previous period, and therepresentations included in the selected subset are filtered inaccordance with the ids of the representations selected at the previousperiod.

Further, the function of the subsets is to enable the selection ofrepresentation groups (a group of) as a single unit, and the selectionof subsets is functionally the same as selections in units ofrepresentation groups. Therefore, when the aforementioned orders ofpriority are put together, the selection which may be performedaccording to the continuity at the representation group level is onlythe case such in (b) of the same figure in which the subsets are notselected.

According to (b) of the same figure, selection of subsets at the periodafter transitioning on the basis of the subset selected at the periodbefore transitioning is not performed. According to this example, therepresentation group with the same id as the representation groupselected at the period before transitioning (or another representationgroup specified in this representation group) is selected.

Also, the representation with the same id as the representation selectedat the period before transitioning (or another representation specifiedby this representation) is selected. However, when the representationselected at the period before transitioning is not included in therepresentation group previously selected, another representationincluded in this representation group is selected.

That is to say, the selection according to the continuity at therepresentation level is performed for further filtering within a rangeso that there are no contradictions in selections at the subset and therepresentation group level.

Also, as illustrated in (c) in the same figure, when the selection isnot performed on the basis of the subsets and the representation groupsselected at the period before transitioning, the client 1 selects therepresentation with the same id as the representation selected at theperiod before transitioning (or another representation specified in thisrepresentation).

In this way, when performing a selection on the basis of only therepresentation selected at the period before transitioning, therepresentation is selected regardless of the subsets and representationgroups selected at the period before transitioning.

Therefore, the selection of the representation in this case is theselection by conditions narrower than that for the subsets andrepresentation groups. That is to say, even when the subset and therepresentation group is determined, there are cases when the client 1does not determine the content to be played, but if the representationis determined, the content to be played by the client 1 is certainlydetermined.

For this reason, regarding a case such as clearly specifying therepresentation to be selected at the next period by the next attributeor the previous attribute, the client 1 may perform a selection of therepresentation, as that with the highest priority, selected at theperiod before transitioning for the period after transitioning.

However, in this case, the all ids of the representations have to bedifferent (one representation corresponding to one specified id isuniquely determined). Also, in this case, the creator of the MPD has todesign the MPD so that there are no contradictions between theselections at the representation level and the selections at the subsetand representation group level.

[MPD Generation by the Server 2]

The MPDs used regarding the aforementioned embodiments may be generatedby the description information transmitting unit 23 in the server 2.Here, the processing to generate the MPD by the description informationtransmitting unit 23 will be described.

For example, for an MPD such as that illustrated in FIG. 2, in contrastto the MPD according to the related art in which the attributesrepresenting subset ids are not included, the description informationtransmitting unit 23 may generate by adding attributes representingsubset ids.

In this case, the description information transmitting unit 23 maydetermine the id of each subset so that the subsets to be continuouslyselected have the same id regarding the subsets included in each period.The description information transmitting unit 23 may write the same idin the subsets forming a combination of the same groups. For example, anid=1 may be written to the subset including groups “1” and “2”, and maywrite an id=2 to the subset including groups “3” and “4”.

Also, the description information transmitting unit 23 writes the sameid to the subsets desired to be selected continuously even for differentcombinations of groups. For example, the same id is written toadvertising content or other to be inserted and played immediatelybefore, immediately after, or during a main content such as video.

In this way, the description information transmitting unit 23 determinesthe identification information (id) for identifying content to be playedat the period of that to be played next corresponding to the contentselected at a certain period.

However, as such situations as the usage language switching duringplayback of content (for example, switching the dialogue from Japaneseto English) are not desirable, the description information transmittingunit 23 writes the same id to subsets representing the combination ofgroups satisfying predetermined conditions.

Other than sharing the usage language, for example, that which may beapplied as these conditions are optional parameters such as the sharingof playback forms of content (for example, 2D displays and 3D displays).Further, the usage language and playback forms may be identified byreferencing attributes or other included in the representation.

The id written in each subset may be automatically determined by thedescription information transmitting unit 23, or may be determined bythe user of the server 2. When determined by the user, an input unit toreceive user operation is provisioned to the server 2, and thedescription information transmitting unit 23 writes the subset id inaccordance with the user operation received by this input unit.

Also, the processing for writing the same id to the subsets forming thecombination of the same groups may be automatically performed by thedescription information transmitting unit 23, or the portions to whichthe same id is to written regarding different combinations of groups maybe written according to user operation.

Further, when selecting the representation groups and the representationat the period after transitioning on the basis of the id of therepresentation group and the representation selected at the periodbefore transitioning, the description information transmitting unit 23shares the id of the representation groups and the representations to becontinuously played when transitioning between periods.

Similar to the case when writing the id to the subset, in this case aswell, the description information transmitting unit 23 automaticallydetermines the id and may generate the MPD to which the determined idsare written by a method in which the same ids are written only whenpredetermined conditions are satisfied.

As the conditions when determining the id of representation groups, forexample, conditions including the representations with the same id maybe used. Also, as the conditions when determined the representation ids,for example, conditions in which playback quality are the sharedrepresentations (representations which at least one parameterdetermining playback quality such as resolution or bit rate is the same)may be used.

Also, the description information transmitting unit 23 may write,automatically or in accordance with user operation, informationrepresenting the continuity of subsets, representation groups, andrepresentations, such as the next attribute and the previous attribute.As an example of writing this automatically, when it is understood thatthere are multiple candidates in the subsets to be played continuously,for example, the known, multiple candidates may be combined by the nextattribute or the previous attribute.

Further, the description information transmitting unit 23 may add thesubset with the id=0 when generating the MPD by modifying the MPDaccording to the related art in which groups included in all subsets arenot clearly defined. Specifically, the description informationtransmitting unit 23 confirms whether or not there are groups notincluded in any of the subsets, and when these exist, the subset withthe id=0 specifying these groups is added. Also, instead of adding thesubset with the id=0, the description information transmitting unit 23may add the groups not included in any subset to all subsets.

Further, the device for generating the MPD is not limited to the server2, and so a device different from the server 2 may perform thegeneration. In this case, the information generated by this device maybe transmitted to the client 1 through the server 2, or may betransmitted to the client 1 directly from this device. Further, arecording medium for recording the information generated by this deviceis provided to the client 1, and the client 1 may read out theinformation from this recording medium.

Fourth Embodiment

According to the aforementioned embodiments, subsets to be playedcontinuously may be uniquely identified by adding a shared id to thesubsets belonging to each period, and so this enabled the simplificationof the processing to analyze the MPD. In this way, by specifying thesubsets to be played, or by restricting that which is to be analyzed inthe MPD, the analysis range of the MPD may be filtered, and theprocessing to analyze the MPD may be simplified.

According to the present embodiment, an example in which the range ofthat to be analyzed in the MPD is restricted by an external performanceof specifying that to be played, in which this enables thesimplification of the processing to analyze the MPD is described withFIG. 20 through FIG. 27 as a basis. Further, the configuration of thesystem and devices is the same as that for the first Embodiment (referto FIG. 1).

As a method for specifying that to be played externally, an examplecould be thought of in which information identifying that to be playedis written to a file such as a web page that can be viewed by the client1. In this case, the client 1 references this information, and acquiresand plays that to be played as identified from the server 2. Further,the information identifying that to be played can be said to beinformation for identifying the analysis range of the MPD.

In the case of such a configuration, as in the example in FIG. 20, forexample, the information for identifying that to be played may bewritten in an HTML document. FIG. 20 is a diagram illustrating anexample of an HTML document to which a URL (analysis rangeidentification information) specifying the subset to be played iswritten.

According to the example in FIG. 20, three URLs,http://example.com/content1.mpd#id=s1,http://example.com/content1.mpd#id=s2, andhttp://example.com/content1.mpd#id=sn, are written. These are videoobject URLs to be played by the client 1.

The shared part of these URLs, “http://example.com/content1.mpd”,represents the MPD to be played. Also, information identifying that tobe played in this MPD is written after the pound sign. Specifically, theid of the subset to be played (analysis range specification information)is written in the format of “id=“id attribute value of that to beplayed””.

That is to say, according to the illustrated URLs, the subsets withids=s1, s2, and sn are specified in order from the top. In this way, bydifferentiating the specified subsets, the content to be played also hasdifferent contents as discussed regarding the differences betweendialogue languages, camera angles, etc., for example. That is to say,the creator who created the content to have multiple playable patternsmay present pattern selections to the user before starting the playbackof content by creating URLS as previously described beforehand.

This kind of HTML document may be created together with the content andthe MPD by the creator of the content, for example. Also, these HTMLdocuments have to be made publicly available to enable the client 1 toview them. For example, when the client 1 accesses this HTML document, amenu screen including selection items (images such as icons and so on)corresponding to each URL or the text of each URL may be displayed toenable the user of the client 1 to select each URL included in this HTMLdocument. As a result, the user may readily select the content accordingto the desired playback pattern. Further, the client 1 is provisionedwith an input unit to receive user operation such as that previouslydescribed.

Next, the processing when a URL included in the aforementioned HTMLdocument is selected will be described with FIG. 21 as a basis. FIG. 21is a diagram illustrating a relationship between a selected URL and theanalysis range of the MPD identified from this URL.

As illustrated, the selected URL is“http://example.com/content1.mpd#id=s2”, and this is the second URL fromthe top in FIG. 20. The content selection unit 13 in the client 1identifies that the MPD to be played is“http://example.com/content1.mpd” from this URL, and obtains this MPD.Further, the destination for obtaining the MPD and the method forobtaining this is not particularly limited, and so a request may be sentto the server 2 to obtain this, for example.

Also, the content selection unit 13 identifies that the subset with theid=s2 is specified as that to be selected from that which is writtenafter the pound sign in the selection URL (#id=s2). The specification ofthis subset is that which specifies the analysis range of the MPD, andas a result, the analysis range of the MPD is specified. That is to say,the content selection unit 13 according to the present embodimentfunctions as means configured to acquire information identifying theanalysis range. Also, the content selection unit 13 performs theanalysis of the MPD after performing the aforementioned identification.

Regarding the analysis of the MPD for the first period, the contentselection unit 13 does not perform the analysis processing on subsetsbesides the subset S_12 to which is written the id=s2 specified by theURL, and only performs the analysis processing on the subset S_12.

Here, the subset S_12 is configured with representation groups whichhave the group attribute of g1 and g3. For this reason, the contentselection unit 13 analyzes the representation groups G11 and G13 towhich group=“g1” and group=“g3” are written, and identifies therepresentations belonging to these representation groups as that to beplayed. Of course, the analysis processing of other representationgroups included in the first period is not performed.

Afterwards, the content selection unit 13 obtains and plays the contenton the basis of the identified representations. Further, afteridentifying the representations, the processing until the playback ofthe content is the same as described regarding the aforementionedembodiments, and so their descriptions are omitted here.

After playback of the first period finishes, the content selection unit13 similarly analyzes the subset S_22 to which the id=“s2” is writtenregarding the second period. Also, the representation groups G21 and G23configuring the subset S_22 are analyzed, and the representationsbelonging to these representation groups are identified as that to beplayed. The same processing is repeated for the following periods.

In this way, by specifying the subsets to be played using URLdescriptions, the analysis processing of the MPD may be simplified evenfor the first period. Also, as in the example in FIG. 20, by writing theselection candidate URLs in an HTML document, selections may be providedto the user before playback is started.

[Specifications by Other Attribute Information]

According to the examples in FIGS. 20 and 21, the subset id has beenused in the specification of that to be played in the URL descriptions,but other attribute information in the MPD may be used to specify thatto be played. That is to say, other attribute information in the MPD maybe used as the information for specifying the analysis range. Here,examples in which attribute information other than the subset id is usedto specify that to be played will be described with FIG. 22 and FIG. 23as a basis.

FIG. 22 is a diagram illustrating a relationship between a URL using agroup attribute value in the specification of that to be played and theanalysis range of the MPD identified from this URL. According to the URLdescription in the same figure, the specification of that to be playedis performed with a format of “id=“applicable attribute name replacingthe id attribute”:“attribute value of that to be played””. That is tosay, the id=group:g1 is the specification for selecting g1 as the groupattribute value of the representation group, and similarly, theid=group:g3 is the specification for selecting g3 as the group attributevalue.

The content selection unit 13, which analyzes the MPD illustrated in thesame figure in accordance with this URL description, does not performanalysis of the subsets in the first period, and analyzes therepresentation group G11 to which group=“g1” is written and therepresentation group G13 to which group=“g3” is written, on the basis ofthe specification of the group attribute. Also, the representationsbelonging to these representation groups are identified as that to beplayed.

Here, according to the example MPD in FIG. 21, the group attributevalues of the representation group configuring the subset with the id=s2are g1 and g3, which are shared in each period. That is to say, thatspecified by the URL description in FIG. 21 and FIG. 22 are the same. Inthis way, a shared group value is added to groups to be playedcontinuously between periods predetermined by the content creator, andthat to be played may be identified in the same way as with the subsetid by referencing these group attributes externally.

After the playback of the first period finishes, in the same way as withthe second period, analysis of the subsets is not performed, therepresentation groups G21 and G23 are analyzed, and playback of therepresentations belonging to these representation groups is performed.The same processing is repeated for the following periods.

Also, in the same way as that in FIG. 21 and FIG. 22, that to be playedmay be specified by using an attribute value shared in each period inthe specification of that to be played in the URL description. This willbe described with FIG. 23 as a basis.

FIG. 23 is a diagram illustrating a relationship between a URLspecifying that to be played using a language attribute (lang attribute)for representation groups and the analysis range for the MPD specifiedfrom this URL. Similar to the example in FIG. 22, the description of theURL in the same figure performs the specification of that to be playedin a format of “id=“applicable attribute name replacing the idattribute”:“attribute value of that to be played””. That is to say, theURL description in FIG. 23 includes a specification for selecting g1 asthe group attribute value of the representation group, and aspecification for selecting en (English) as the lang attribute value ofthe representation group.

The content selection unit 13, which analyzes the MPD illustrated in thesame figure in accordance with this URL description does not performanalysis of the subsets in the first period, and analyzes therepresentation group G11 to which group=“g1” is written and therepresentation group G13 to which lang=“en” is written, on the basis ofthe specification of the group attribute. Also, the representationsbelonging to these representation groups are identified as that to beplayed. A similar selection is performed for the following periods. Thatis to say, a playback similar to that as in FIG. 21 and FIG. 22 isperformed.

Further, though examples in which that to be played is specified using ashared attribute value for the representation groups have beenillustrated as previously described, that to be played may also besimilarly specified using a shared attribute value for therepresentations.

[Specifying the Period for that to be Played]

As previously described, examples in which only the subsets to be played(or representation groups or representations) are specified have beendescribed, but in addition to the specification of that to be played,the playback position of the content (period of that to be played) mayalso be specified. That is to say, the information for identifying thatto be analyzed, which is obtained by the client 1 by a format such as aURL or other, may also include information for specifying the period ofthat to be played, which specifies the playback period (period) of thatto be analyzed in the MPD. As a result, a digest playback may be enabledin which only a portion of the content playback period is played.

For example, the playback period (playback time) may be specified in theURL description with a format of “t=“playback start time”, “playback endtime””. In this case, the content selection unit 13 identifies therepresentation in which the playback start time to the playback end timeis specified by this URL description, and obtains the content for thistime. Further, content may be obtained in the same way in cases when theplayback time is not specified, and so by notifying the content playbackunit 15 of the aforementioned playback start time and playback end time,playback of content for this time may be enabled.

Also, the period for that to be played may be specified using the idattribute in the MPD in the same way as specifying the subset of that tobe played (or the representation group or the representation). This willbe described with FIG. 24 as a basis.

FIG. 24 is a diagram illustrating a relationship between a URLspecifying the period of that to be played by a period id and theanalysis range of the MPD identified from this URL. According to the URLdescription in the same figure, sports news (id=sprots) and a weatherforecast (id=weather) are specified as that to be played within the MPDrepresenting a configuration of a news program(http://example.com/news.mpd). That is to say, the time for the sportsnews and the time for the weather forecast is specified as the periodfor that to be played.

The content selection unit 13, which analyzes the MPD illustrated in thesame figure in accordance with this URL description, designates only theperiods that have the specified id attribute (P1 and P2 in the samefigure) as that to be analyzed. That is to say, analysis of the subsets,representation groups, and representations in this period is performed,and the representations are identified. As a result, only the sportsnews and weather forecast from the news program content is played as adigest.

Further, when specifying the period for that to be played by URLs, thismay be specified with the format of “id=“id attribute value representingthe playback start position”, “id attribute value representing theplayback end position”” instead of the aforementioned “id=“id attributevalue of that to be played”” in order to simplify the specification ofmultiple periods for that to be played.

For example, when the description specifying the period for that to beplayed in the URL description in FIG. 24 (description after the poundsign) is “id=sport,weather”, this description represents that a sequenceof content from the sports news to the weather forecast is to be played.Therefore, the content selection unit 13, which analyzes the MPD inaccordance with this URL description, analyzes from P1 to P2 inaccordance with the specification “id=sport,weather”. As a result, thesequence of content corresponding to this analysis range (contentincluded in three periods represented by id=sport, id=entertainment, andid=weather) is played.

Also, between the “id attribute value representing the playback startposition” and the “id attribute value representing the playback endposition”, one of these may be omitted. For example, using thedescription “id=,weather” in which the specification of “id attributevalue representing the playback start position” is omitted, playbackfrom the first period until the weather forecast (P2) is specified.Also, when using the description “id=sports,” in which the specificationof “id attribute value representing the playback end position” isomitted, playback from the sports news (P1) and all following periodsbecomes the period for that to be played.

Here, when specifying the period for that to be played using the periodid, the position during a period cannot be used to specify the playbackstart or end time, and so the performance of fine time specificationscannot be performed. However, as in the example in FIG. 24, byprovisioning rules for adding the id depending on the part of thepredetermined video content, and determining the URLs for digestplayback depending on these parts beforehand, general specification ofthe periods for that to be played using the period id are enabled.

That is to say, as in the example of the aforementioned news program, arule for adding the “id=sports” to the sports news is provisioned, andthe “id=sports” is written in the URL. As a result, the client 1, whichfollows this rule, may perform the digest playback of only the sportsnews. Also, by previously preparing a digest playback selection menu ofthe different parts formatted as an HTML document or other, the user mayselect the desired parts.

[Playback when Both that to be Played and the Period of that to bePlayed are Specified]

Next, the playback processing at the client 1 when both thespecification of the subsets to be played (or representation groups orrepresentations) and the specification of the periods for that to beplayed are specified at the same time will be described with FIG. 25 andFIG. 26 as a basis.

FIG. 25 is a diagram illustrating a relationship between a URLspecifying the subsets to be played and the periods for that to beplayed and the analysis range of the MPD identified from this URL. Also,FIG. 26 is a diagram illustrating that to be analyzed as identified fromthe URL description in FIG. 25.

The URL in the example in FIG. 25 describes the MPD to be played as“http://example.com/content1.mpd”. Also, this URL describes the periodfor that to be played as “id=p2,”. As previously described, thisspecifies the period with the id=p2 and the periods following as theperiod for that to be played. Also, that to be played is described as“id=s2”. As previously described, this specifies the subset with theid=s2.

In this way, when specifying both the period for that to be played andthat to be played, the client 1 performs playback of that to be playedincluded in the specified period for that to be played, as illustratedin FIG. 26. That is to say, the content selection unit 13 designates thesubsets with the id=s2 as that to be analyzed from the period with theid of p2 and the periods following. According to the example, the subsetwith the id of s2 includes the representation groups with the groupattribute of g1 and g3, and so g1 and g3 become that to be analyzed, andthe content corresponding to the representations included in thesebecome that to be played.

That is to say, according to the example in FIG. 25, as the period withthe id of p2 and the periods following are designated as the period forthat to be played, the content selection unit 13 does not performanalysis within the first period, which does not have the id of p2, anddesignates the second period (P2) to which the id=“p2” is written andthe following periods as that to be analyzed.

Also, in period P2 only the subset S_22 to which the id=“s2” is writtenis designated as that to be analyzed, and so analysis processing is notperformed on any other subsets. Specifically, the subset S_22 isconfigured by the representation groups with the group attribute of g1and g3. For this reason, the content selection unit 13 analyzes therepresentation groups G21 and G23 to which the group=“g1” and group=“g3”are written, and identifies the representations belonging to theserepresentation groups. Of course, the analysis processing is notperformed on the other representation groups included in the period P2.A similar processing is repeated for the following periods, which arethe periods for that to be played.

As previously described, by using URLs specifying the subsets to beplayed (or representation groups or representations) and the periods forthat to be played, a digest playback of content may be performed. Also,by writing these URLs to an external HTML document or other, this may beused as a content selection menu. Also, similar to the aforementionedembodiments, by restricting the MPD analysis range during playback, theMPD analysis processing may be simplified.

[Example of Using that Other than URL Specifications]

As previously described, URLs specifying the subsets to be played (orrepresentation groups or representations) and the periods for that to beplayed may be used as a content selection menu for the user.

Also, these URLs may be used as information for identifying the playbackstart position in such cases as when playback is interrupted on theclient 1 and restarts, or when playing on a different playback deviceand handing over the playback state. That is to say, the client 1generates the content that has been playing and the URL identifying theinterruption position of playback, and may restart playback at theplayback state at the time of the interruption by referencing this whenrestarting playback. Also, by notifying these URLs to other playbackdevices, the playback state may be handed over to these other playbackdevices.

For example, it can be though to generate these kinds of URLs and notifythem to a playback device when the client 1 is a device with acomparatively small screen such as a smartphone, and the contentcurrently playing on this device is desired, by user operation, to behanded over and played on a playback device with a relatively largescreen such as a television.

The generation of URLs for handing over the playback state will bedescribed with FIG. 27 as a basis. FIG. 27 is a diagram illustrating anexample of a playback position in the MPD to be played, and a URLgenerated when playback is interrupted at this playback position.

According to the illustrated example, the MPD to be played is“http://example.com/content1.mpd”, and represents that the mediasegments corresponding to the representations R1 and R2 are currentlyplaying by the content playback unit 15 in the client 1. Further, therepresentations R1 and R2 are included in the period beginning fromPT300S, and after 100 seconds has passed since the playback of thecontent corresponding to the representations R1 and R2 has started, theplayback time becomes PT400S.

Regarding this kind of playback state, when user operation is performedto play the currently playing content on another device (when a requestto notify the playback state is generated), the content playback unit 15in the client 1 generates a URL corresponding to the playback positionat this time. That is to say, according to the present embodiment, thecontent playback unit 15 functions as means configured to generateinformation to identify the analysis range, which identifies theanalysis range of the MPD. Of course, means configured to generateinformation to identify the analysis range may be provisioned assomething other than the content playback unit 15.

According to the example in FIG. 27, the currently playingrepresentation R1 is a representation belonging to the representationgroup G21, and the representation R2 is a representation belonging tothe representation group G23. Also, the representation groups G21 andG23 are the representation groups configuring the subset S_22.Therefore, the content playback unit 15 determines that the subset to beplayed is specified with the “id=s2”.

Also, it is determined that the range of that to be played after theplayback restarts is specified as “t=400,” from the fact that theplayback time is PT400S. Also, the MPD to be played ishttp://example.com/content1.mpd.

Therefore, the content playback unit 15 generates“http://example.com/content1,mpd#id=s2&t=400,” as the URL to be notifiedto the playback device to which the playback of content is handed over.Also, the content playback unit 15 notifies this URL to the playbackdevice in accordance with the user request.

At the playback device receiving this notification, analysis of theperiods in which the playback start time is after PT400S starts on thebasis of the notified URL. Specifically, the analysis processing isperformed on the subset S_22 to be played to which the id=“s2” iswritten as specified by the aforementioned URL from the subsets includedin the periods after PT400S. That is to say, the content playback unit15 functions as means configured to transmit identification information.Of course, means configured to transmit identification information otherthan the content playback unit 15 may be provisioned.

Next, the aforementioned playback device analyzes the representationgroups G21 and G23 configuring the subset S_22. Also, therepresentations belonging to these representation groups are selected,and playback after PT400S is started. As a result, the playback state atthe client 1 is handed over to the playback device.

Further, playback of other representations belonging to therepresentation groups G21 and G23 not limited to the representations R1and R2 that have been playing on the client 1 may be allowed on theplayback device to which the playback state of the client 1 has beenhanded over depending on the playback performance of the device, thecommunication environment, and so on.

Also, though the subset id specifying that to be played has been usedaccording to the aforementioned example, the specification of that to beplayed using the group attribute for the representation groups and therepresentation ids is also possible.

Fifth Embodiment

The MPD according to the aforementioned embodiments is one complete MPDthat does not reference external data, but various types of playbackbecome possible by referencing external data. According to the presentembodiment, an example in which playback is performed using an MPD thatreferences other MPDs will be described with FIG. 28 through FIG. 30 asa basis. Further, the configuration of the system and devices is thesame as that for the first Embodiment (refer to FIG. 1).

Here, when describing that to be played using an HTML document, asdescribed with FIG. 20 as a basis, the user may be allowed to makeselections by displaying images such as URL text and icons. However,according to this configuration, the user has to decide whether or notto select some content from only the limited information obtainable fromthe text and icons, and so it may be thought that sometimes undesirablecontent is selected. This is because the content corresponding to theprovided text cannot be viewed until after this text and so on isselected.

Thus, the client 1 according to the present embodiment provides contentto be selected as video by using MPDs (content information on that to beselected) to which externally referenced URLs (information forspecifying a change destination) pointing to other MPDs (information forselecting a change destination) in each period are written. In this way,the aforementioned problem may be resolved by the content to be selectedas video content instead of text, icons, and so on.

First, the MPD referenced by the client 1 will be described with FIG. 28as a basis. FIG. 28 is a diagram illustrating an example of an MPD whichreferences other MPDs. In FIG. 28, the URL of the MPD to be externallyreferenced is written into each period with a format of “xlink:href=“URLof the destination to be externally referenced””. For example, for theperiod to which id=“period11” is written, the“http://example.com/Dorama_Ep1mpd#id=period1,” is the URL for the MPDset to the externally referenced destination. More specifically, the“http://example.com/Dorama_Ep1mpd” from this URL specifies the MPD, andthe “#id=period1,” specifies the playback position in this MPD. That isto say, the “#id=period1,” may be said to be the information specifyingthe playback position.

Further, the “xlink” is normally used to embed the external data intothe MPD at the description position of the “xlink”, and this isinterpreted at the default state to perform an embedding of data.However, according to the present embodiment, the “xlink” referencesother MPDs, and is used for a purpose different from normal usage, inwhich a change in that to be played is performed. For this reason,according to the illustrated MPD, “xlink:show=“new”” is written asinformation representing that this will be used for a new purposeinstead of the default purpose.

When performing a playback using this kind of MPD, the client 1 performsan operation to change that to be played to the content identified bythe URL for the externally reference destination in the period when apredetermined user operation is performed during playback of thisperiod. As a result, it is possible to use the video content (MPD) as aselection menu.

Here, an example using the video content (MPD) as a selection menu willbe described with FIG. 29 as a basis. FIG. 29 is a diagram illustratinga reference relationship between a period of a drama main feature and aperiod of a digest video in a case when the digest video of the dramamain feature is used as a selection menu. According to this kind ofcontent, the content selected at each period may be expressed as aportional content configuring a portion of the content such as the dramamain feature or the digest video.

The same figure illustrates an MPD (Drama_Ep1.mpd through Drama_EpN.mpd)representing the drama main feature (the first episode through the nthepisode) and an MPD (Digest.mpd) representing a digest videocorresponding to each drama main feature (the first episode through thenth episode of the dram main feature). The user may perform playbackchanging from this digest video to the drama main feature. That is tosay, the digest video is used as a selection menu of the drama mainfeature.

According to this example, externally referenced URLs instructing theplayback of a corresponding scene of the main drama feature(corresponding period) and the following scenes are written into eachperiod configuring the digest video (Period11 through PeriodN3). Forexample, an externally referenced URL instructing the playback ofPeriod1 of the drama main feature and the following periods as that tobe played is written into Period11 of the MPD for the digest video(refer to FIG. 28).

Also according to this example, externally referenced URLs instructingthe playback of the period corresponding to the digest video and thefollowing periods are written into the each period of the dram mainfeature. Further, regarding the MPD of the dram main feature, externallyreferenced URLs specifying the MPD of the corresponding digest video arewritten into each period in the same format as for the MPD of the digestvideo illustrated in FIG. 28. For example, an externally reference URLspecifying Period11 of the digest video and the following periods asthat to be played is written in Period1 of the first episode of thedrama main feature.

According to the example in FIG. 29, externally referenced URLsspecifying the corresponding periods are written into the MPDs of boththe drama main feature and the digest video in this way. As a result,the MPD of the drama main feature and the MPD of the digest video aremutually referenced as illustrated by the arrows in the same figure.

At the client 1 performing playback using these kinds of MPDs, when apredetermined user operation (a button pressing or similar) is performedinstructing the change to the main feature during the playback of thedigest video as the selection menu, playback is changed to thecorresponding scene (corresponding period) of the drama main feature.Also, the following scenes continue to be played after thiscorresponding scene finished playback.

Specifically, when the content selection unit 13 in the client 1 detectsthat the aforementioned user operation has been performed, the periodsplayed by the content playback unit 15 at this time are identified.Next, the content selection unit 13 obtains the MPD specified by theexternally referenced URL included in the identified period. Also, thecontent selection unit 13 identifies the periods to be played that arespecified by the aforementioned externally referenced URL for this MPD.As a result, the content of the identified periods are played. Also, thefollowing periods continue to be played after this period finishedplayback.

Similarly, when user operation is performed to change to the digestvideo during playback of the drama main feature, playback is changed tothe corresponding scene (corresponding period) of the digest video.Also, the following scenes continue to be played after thiscorresponding scene finishes playback.

As previously described, video content may be used as the selection menuby specifying the change destination of the period with externallyreferenced URLs.

[Example of Using Specifications Other than URLs]

According to the examples in FIG. 28 and FIG. 29, the specification ofthe change destinations with externally referenced URLs is performed inunits of periods, and mutual referencing is performed in units ofperiods, a configuration may perform mutual referencing in finer unitssuch as units of media segments. However, as the need arises to writemany externally referenced URLs in order to perform mutual referencingat units finer than units of periods, it is desirable to simplify thesedescriptions using a method such as with the example illustrated in FIG.30.

FIG. 30 is a diagram illustrating an example of an MPD performing thespecification of MPD change destinations in units of media segments.According to the MPD (http://example.com/content1_ff.mpd) in (a) of FIG.30, “http://example.com/content1_ff.mpd#t=idx:$idx,” is written as theexternally referenced URL for the period. Also, the identificationinformation for identifying media segments is written into each mediasegment with a format of “idx=“identification number””. Further, the MPD(http://example.com/content1_ff.mpd) specified by this externallyreferenced URL is illustrated in (b) of the same figure.

Here, the “t=idx:” in the aforementioned externally referenced URL isthe specification using a segment index to specify the periods for thatto be played, and the “$idx” is the specification designating thesegment index value of the media segment currently playing as aparameter. Further, according to the example in FIG. 30, there is a “,”after the “$idx”, and as previously described, this is the descriptionformat when specifying only the playback start position. That is to say,according to this example, the media segments following the segmentindex value designated as the parameter also become that to bespecified.

The externally referenced URL is specified depending on the mediasegment currently playing by this specification of “t=idx:$idx,”. Forexample, when the media segment represented by the <Url sourceURL=“content1_seg5.3gs” idx=5/> in (a) of the same figure is currentlyplaying, the “5”, which is the segment index value of this media segmentbecomes the parameter. That is to say, the externally referenced URL is“http://example.com/content1_ff.mpd#t=idx:5,”.

Therefore, when a predetermined user operation for performing the changeis performed during the playback of the <Url sourceURL=“content1_seg5.3gs” idx=5/> media segment, as illustrated the arrowsin the same figure, playback switches to the corresponding media segment<Url source URL=“ff_seg5.3gs” idx=5/> in (b) of the same figure. Also,continued playback of media segments following after this is performedafter this media segment finishes playback.

Specifically, when the content selection unit 13 in the client 1 detectsthat the aforementioned user operation has been performed, the MPDspecified by the “xlink:href=” in the MPD currently under analysis isobtained. Also, the segment index value of the media segment played bythe content playback unit 15 at this time is identified. Also, the mediasegment of the aforementioned and identified segment index value isidentified in the aforementioned and obtained MPD are identified as thatto be played. As a result, the identified media segment is played. Also,the following media segments continue to be played after this mediasegment finished playback.

Similarly, when a similar user operation is performed during playback ofthe media segment <Url source URL=“ff_seg5.3gs” idx=5/> in (b) of thesame figure, as illustrated by the arrows in the same figure, playbackchanges to the corresponding media segment <Url sourceURL=“content1_seg5.3gs” idx=5/> in (a) of the same figure. Also,continued playback of media segments following after this is performedafter this media segment finishes playback.

In this way, descriptions may be simplified as compared to a case whenspecifying media segments individually by designating the externallyreferenced URL to specify the media segment with the same segment indexvalue as the media segment currently playing.

Also as illustrated in the example in FIG. 30, a trick play may beperformed by freely changing the playback speed of the content by usingan MPD performing mutual referencing in units of media segments.

For example, let us assume that (a) in FIG. 30 is video content atnormal playback speed, and (b) of the same figure is video contentcorresponding to a playback speed of 10 times that of the video contentin (a). In this case, a playback in which the normal playback video andthe playback video at 10-time speed is mutually changed is enabled bymutual referencing between these corresponding media segments. That isto say, an operation equivalent to a difficult trick play (changing ofarbitrary timings between high-speed playback and normal playback)regarding normal streaming playback is achieved. Of course, in thiscase, the idx included in each MPD has to be set regarding the mediasegments corresponding to (matching) idx so that the same content isplayed at different playback speeds.

[Obtaining the Content]

According to the aforementioned embodiments, examples have beendescribed in which content has been obtained by requesting the server 2,but a configuration in which content is obtained without requests iswithin the scope of the present invention. For example, contentdelivered as a multicast, or content transmitted by broadcasting may bereceived and played in accordance with the selection of the contentselection unit 13.

With such a configuration, content to be played at a certain playbackperiod may be selected by referencing the MPD according to theaforementioned embodiments, and at the same time, the content to beplayed at the playback period to be played next may be readily selected.

[About the Data Structure of Combined Information and the RecordingMedium for Recording the Combined Information]

The data structure of the information representing the continuity ofcontent when transitioning between periods, the information representinggroups included in all subsets, and description information including atleast some kind of information for referencing other descriptioninformation as previously described (e.g., MPD), the recording mediumrecording the description information, and the method for generating thedescription information are included in the scope of the presentinvention.

As this recording medium, for example, tape such as magnetic tape andcassette tape, disks including magnetic disk such as floppy disk(registered trademark) and hard disk, and optical disk such as CD-ROM,MO, MD, DVD, BD, and CD-R, cards such as IC cards (including memorycards) and optical cards, semiconductor memory such as mask ROM, EPROM,EEPROM, and flash ROM, and logical circuits such as PLD (Programmablelogic device) and FPGA (Field Programmable Gate Array) may be used.

[About Combinations of the Embodiments]

The present invention is not limited to the aforementioned embodiments,various modification under the scope represented by the claims arepossible, and the technical scope of the present invention includesembodiments obtained by desirable combinations of technical methodsdisclosed in the different embodiments. Also, the scope of the presentinvention also includes optional configurations as combinations ofconfigurations of the different embodiments such as writing informationfor referencing other MPDs to the MPD including an id specifying thesubset to be selected at the next period.

[Example Configuration by Software]

Lastly, each block of the client 1 and the server 2 may be achieved byhardware of logical circuits in which the client control unit 10 and theserver control unit 20 in particular are formed on integrated circuits(IC chips), or may be achieved as software using a CPU (CentralProcessing Unit).

In the case of the latter, the client 1 and the server 2 are provisionedwith a CPU for executing instructions of a program for achieving eachfunction, ROM (Read Only Memory) for storing the aforementioned program,RAM (Random Access Memory) for deploying the aforementioned program, astorage device (storage medium) such as memory for storing theaforementioned program and various data, and so on. Also, the object ofthe present invention is also attainable by providing, to the client 1and server 2, a recording medium to which program code (executableformat program, intermediate code program, and source program) of acontrol program of the client 1 and server 2 in which the aforementionedfunctions are achieved as software is recorded in a computer-readableformat, and reading and executing the program code recorded in therecording medium by this computer (or CPU, or MPU).

As the aforementioned recording medium, for example, tape such asmagnetic tape and cassette tape, disks including magnetic disk such asfloppy disk (registered trademark) and hard disk, and optical disk suchas CD-ROM, MO, MD, DVD, BD, and CD-R, cards such as IC cards (includingmemory cards) and optical cards, semiconductor memory such as mask ROM,EPROM, EEPROM, and flash ROM, and logical circuits such as PLD(Programmable logic device) and FPGA (Field Programmable Gate Array) maybe used.

Also, the client 1 and server 2 may be configured to be connectable to acommunications, and the aforementioned program code may be provided viaa communications network. This communications network is notparticularly limited as long as the program code is transmittable. Forexample, the Internet, intranets, extranets, LAN, ISDN, VAN, CATVcommunication networks, virtual private networks, phone line networks,mobile communication networks, satellite communication networks, and soon may be used. The transmission medium configuring these communicationnetworks is not limited to particular configurations or types as long asthe medium is able to transmit the program code. For example, wiredconnections such as IEEE1394, USB, power line delivery, cable TV lines,phone lines, ADSL (Asymmetric Digital Subscriber Line), infrared such asIrDA and remote controls, and wireless connections such as Bluetooth(registered trademark), IEEE802.11 wireless, HDR (High Data Rate), NFC(Near Field Communication), DLNA (Digital Living Network Alliance),cellular phone networks, satellite lines, terrestrial digital networks,and so on may be used. Further, the present invention may be implementedas a form of computer data signal embedded in a carrier which embodiesthe aforementioned program code as an electronic transmission.

[Conclusion]

The playback device disclosed in the aforementioned embodiments obtainsand plays content selected after referencing content information on thatto be selected including information representing acquirable content ineach playback period of the content, in which identification informationfor identifying content to be played at the playback period to be playednext corresponding to the content selected at a certain playback periodis included in the aforementioned content information on that to beselected, and this playback device includes selection means configuredto select content to be played at the aforementioned certain playbackperiod after referencing the aforementioned content information on thatto be selected, and at the same time, for selecting content to be playedat the playback period to be played next in accordance with theaforementioned identification information, acquisition means configuredto acquire the content selected by the aforementioned selection means,and playback means configured to play content acquired by theaforementioned acquisition means at a certain playback period aspreviously described and for continuously playing the content to beplayed at the playback period to be played next.

The control method for the playback device disclosed in theaforementioned embodiments controls the playback device to obtain andplay content selected after referencing content information on that tobe selected including information representing acquirable content ineach playback period of the content, in which identification informationfor identifying content to be played at the playback period to be playednext corresponding to the content selected at a certain playback periodis included in the aforementioned content information on that to beselected, and this control method includes a selection step forselecting content to be played at a certain playback period afterreferencing the aforementioned content information on that to beselected, and at the same time, for selecting content to be played atthe playback period to be played next in accordance with theaforementioned identification information, an acquisition step foracquiring the content selected by the aforementioned selection step, anda playback step for playing content acquired by the aforementionedacquisition step at a certain playback period as previously describedand for continuously playing the content to be played at the playbackperiod to be played next.

According to the aforementioned configuration, identificationinformation for identifying content to be selected at the playbackperiod to be played next corresponding to the content selected at acertain playback period is included in the aforementioned contentinformation on that to be selected. Also, content to be played at theplayback period to be played next is selected in accordance with thisidentification information, the selected content is acquired and playedduring each playback period.

Therefore, when transitioning from a certain playback period to theplayback period to be played next, content depending on the contentselected at a certain playback period is readily selected, and this maybe acquired and played.

Further, the aforementioned identification information may directlyspecify the content, or may be that for filtering candidates of contentto be selected. Also, when content is selected from filtered contentafter selecting the information filtering the content to be selected ata certain playback period, the aforementioned identification informationmay represent information filtering content to be selected at theplayback period to be played next depending on the information filteringthe content to be selected that was selected at a certain playbackperiod.

Also, a certain playback period and the playback period to be playednext may be playback periods continuing on a timeline such as theplayback period immediately before or immediately after, or may beplayback periods separated on a timeline.

Further, a certain playback period and the playback period to be playednext may be playback periods included in individual content informationon that to be selected. That is to say, when selecting content from aplayback period in the content information on that to be selected afterselecting content from a playback period in the content information onthat to be selected, the content may be selected using theaforementioned identification information.

Also, regarding the aforementioned configuration, the method foracquiring the content is not particularly limited, and for example,content may be received by requesting the server, or content may bereceived as transmitted from the server without the performance of arequest to the server.

Also, it is desirable that the aforementioned content information onthat to be selected includes at least one group specificationinformation per playback period, in which at least one group isspecified such that content belongs to groups wherein content includedin the same group cannot be played simultaneously, but content includedin different groups may be played simultaneously, the aforementionedidentification information includes information specifying the groupspecification information to be selected at the playback period to beplayed next corresponding to the group specification informationselected at a certain playback period, and the aforementioned selectionmeans selects the aforementioned group specification information at acertain playback period, and at the same time, selects the contentbelonging to the group specified by the selected group selectioninformation, and regarding the playback period to be played next, thegroup selection information specified by the aforementionedidentification information to which a correspondence with the groupspecification information selected at a certain playback period aspreviously described is added is selected, and the content belonging tothe group specified by the selected group specification information isselected.

According to the aforementioned configuration, the content informationon that to be selected includes at least one group specificationinformation per playback period specifying at least one group. Also, theplayback device selects the group specification information inaccordance with the information specifying the group specificationinformation to be selected at the playback period to be played nextcorresponding to the group specification information selected at acertain playback period included in the identification information.

By selecting the group specification information, the content to beselected is limited to that belonging to the group specified by thegroup specification information. That is to say, the group specificationinformation may be said to be information filtering the content to beselected. For this reason, according to the aforementionedconfiguration, the content to be selected may be readily filtered, andas a result, the processing load from selecting content is reduced.

Further, as the content included in the same group cannot be playedsimultaneously, one content is selected from one group. Also, it may berequired to select one content from one group, or not selecting contentmay be allowed.

Also, as content included in different groups may be playedsimultaneously, the overall framework of content is determined by thegroup specification information. That is to say, content is determinedat the application level by the selected group specificationinformation.

For example, when the group specification information specifying a groupincluding video content and a group including Japanese dialogue contentis selected, the video and actual dialogue contents changed depending onwhat content is selected from the group, but the playback of videocontent with Japanese dialogue is definitive.

Therefore, according to the aforementioned configuration for selectingthe group specification information, continuity of content may bemaintained at the application level in accordance with the informationspecifying the group specification information to be selected at theplayback period to be played next corresponding to the groupspecification information selected at a certain playback period.

Also, it is desirable that the aforementioned content information onthat to be selected includes group specification information foressential selection representing groups that have to be selected, andthe aforementioned selection means selects the content belonging to thegroup specified by the aforementioned group specification informationfor essential selection as well at the aforementioned playback period tobe played next.

According to the aforementioned configuration, when the group that hasto be selected is not included in the group specification informationselected in accordance with the identification information, the groupthat has to be selected may be reliably selected.

Also, it is desirable that the aforementioned identification informationfurther includes information specifying content to be selected at theplayback period to be played next corresponding to the content selectedat a certain playback period as previously described, and theaforementioned selection means selects the content when the contentspecified by the aforementioned identification information is includedin the group specified by the group specification information selectedat the aforementioned playback period to be played next, and selects thecontent belonging to the group when not included.

According to the aforementioned configuration, the identificationinformation further includes information specifying content to beselected at the playback period to be played next, and so the contentdepending on the content selected at a certain playback period may bereadily selected.

However, when continuity is given priority at the content level, thereis a potential that the continuity at the application level breaks. Forexample, it may be thought that the continuity for the bit rate,resolution, and so on are maintained, but the usage language or other ischanged.

For this reason, according to the aforementioned configuration, thecontent is selected when the content specified by the identificationinformation is included in the group specified by the selected groupidentification information, and the content belonging to the groupspecified by the selected group specification information is selectedwith not included.

As a result, the load caused by the selection of content may be furtherreduced within a range such that the continuity at the application levelis not broken.

Also, it is desirable that the aforementioned content information onthat to be selected includes substitute specification informationrepresenting the group specification information to be selected when thegroup specification information cannot be selected in accordance withthe aforementioned identification information, and the aforementionedselection means selects the group specification information representingthe aforementioned substitute specification information when the groupspecification information cannot be selected in accordance with theaforementioned identification information, and selects the contentbelonging to the group specified by the selected group specificationinformation.

According to the aforementioned configuration, even when the groupselection information specified by the identification information cannotbe selected, there is still no need to have the user select the groupspecification information as the group specification information andcontent is selected in accordance with the substitute specificationinformation. Also, when changing playback periods, continuity of somecontent may be maintained.

Further, cases in which the group specification information cannot beselected in accordance with the identification information, for example,include such cases as when the group specification information specifiedby the identification information is not included in the applicableplayback period, or when a correspondence with the group specificationinformation selected at the playback period before changing is not addedto the identification information.

Also, it is desirable that the aforementioned selection means selectsthe group specification information specified by the aforementionedidentification information at the playback period to be played next whenthe group specification information specified by the aforementionedidentification information to which a correspondence with the groupspecification information selected at a certain playback period aspreviously described is added is not included in the playback period tobe played next, and selects the content belonging to the group specifiedby the selected group specification information.

According to the aforementioned configuration, the group specificationinformation and content specified by the identification information isselected at the playback period to be played next after the playbackperiod when the group specification information and content was selectedin accordance with the substitute specification information.

Therefore, when performing playback in which playback periods notincluding the group specification information specified by theidentification information are sandwiched, continuity of the content maybe maintained.

Also, it is desirable that the aforementioned content information onthat to be selected includes content affiliation information perplayback period, in which at least one content is specified such thatcontent belongs to groups wherein content included in the same groupcannot be played simultaneously, but content included in differentgroups may be played simultaneously, the aforementioned identificationinformation includes information specifying the content affiliationinformation to be selected at the playback period to be played nextcorresponding to the content affiliation information selected at acertain playback period, and the aforementioned selection means selectsthe aforementioned content affiliation information at a certain playbackperiod, and at the same time, selects the content specified by theselected content affiliation information, and regarding the playbackperiod to be played next, the content affiliation information specifiedby the aforementioned identification information is selected, and thecontent represented by the selected content affiliation information isselected.

According to the aforementioned configuration, the content informationon that to be selected includes content affiliation informationrepresenting at least one content included in a group each playbacktime. Also, the playback device selects the content affiliationinformation in accordance with the information specifying the contentaffiliation information to be selected at the playback period to beplayed next corresponding to the content affiliation informationselected at a certain playback period included in the identificationinformation.

By selecting the content affiliation information, the content to beselected is limited to the content represented by the contentaffiliation information. That is to say, the content affiliationinformation may be said to be information filtering the content to beselected. For this reason, according to the aforementionedconfiguration, the content to be selected may be readily filtered, andas a result, the processing load from selecting content is reduced.

Further, the content affiliation information may be included in each ofmultiple, corresponding groups for one playback period, and in thiscase, multiple content affiliation information may be selected at oneplayback period. When selecting multiple content affiliationinformation, the content affiliation information corresponding to thepreviously selected content affiliation information is selected at theplayback period to be played next. Also, the selection of content isperformed for each selected content affiliation information. Further, aslong as at least one content is eventually selected, there may becontent from the selected content affiliation information that is notselected.

Also, the aforementioned content information on that to be selected mayinclude content specification information per playback period specifyingcontent, the aforementioned identification information may includeinformation specifying the content specification information selected atthe playback period to be played next, and the aforementioned selectionmeans may select the content specified by the aforementioned contentspecification information at a certain playback period, and may selectthe content specification information specified by the aforementionedidentification information at the playback period to be played next, andmay select the content specified by the selected content specificationinformation.

According to the aforementioned configuration, content is selected at acertain playback period by the content specification informationincluded in the content information on that to be selected, and thecontent specified by the selected content specification information isselected in accordance with the identification information. Therefore,content may be readily selected at a certain playback period and at theplayback period to be played next.

Also, it is desirable that the identification information included inthe content information on that to be selected in a certain playbackperiod as previously described includes information for identifyingcontent to be selected at the playback period immediately after thiscertain playback period, and when the playback period to be played nextis the playback period immediately after a certain playback period aspreviously described, the aforementioned selection means references theinformation included in the identification information for identifyingthe content to be selected at the playback period immediately after acertain playback period to select the content.

According to the aforementioned configuration, the identificationinformation included in the content information on that to be selectedin a certain playback period included information for specifying contentto be played at the playback period immediately after this certainplayback period. Also, when the playback period to be played next is theplayback period immediately after a certain playback period aspreviously described, the playback device references the informationincluded in the identification information for identifying the contentto be selected at the playback period immediately after a certainplayback period to select the content.

Therefore, the playback device may readily select content depending onthe content selected at a certain playback period for the playbackperiod immediately after a certain playback period.

Further, it is desirable that when the information for identifying thecontent to be selected at the playback period to be played next isincluded in the identification information, regardless of the positionalrelationship regarding the playback time axis between a certain playbackperiod and the playback period to be played next, the information foridentifying the content to be selected at the playback periodimmediately after a certain playback period is given priority to selectthe content.

Also, the information for identifying the content to be selected at theplayback period immediately after a certain playback period may beinformation directly specifying content, or may be that for filteringcandidates of content to be selected. For example, this may beinformation specifying group specification information to be selected,or may be information representing multiple candidates of groupspecification information to be selected.

Also, it is desirable that the identification information included inthe content information on that to be selected in a certain playbackperiod as previously described includes information for identifyingcontent to be selected at the playback period immediately before thiscertain playback period, and when the playback period to be played nextis the playback period immediately before a certain playback period aspreviously described, the aforementioned selection means references theinformation included in the identification information for identifyingthe content to be selected at the playback period immediately before acertain playback period to select the content.

According to the aforementioned configuration, the identificationinformation included in the content information on that to be selectedin a certain playback period included information for specifying contentto be played at the playback period immediately before this certainplayback period. Also, when the playback period to be played next is theplayback period immediately before a certain playback period aspreviously described, the playback device references the informationincluded in the identification information for identifying the contentto be selected at the playback period immediately before a certainplayback period to select the content.

Therefore, the playback device may readily select content depending onthe content selected at a certain playback period for the playbackperiod immediately before a certain playback period.

Further, it is desirable that when the information for identifying thecontent to be selected at the playback period to be played next isincluded in the identification information, regardless of the positionalrelationship regarding the playback time axis between a certain playbackperiod and the playback period to be played next, the information foridentifying the content to be selected at the playback periodimmediately before a certain playback period is given priority to selectthe content.

Also, the information for identifying the content to be selected at theplayback period immediately before a certain playback period may beinformation directly specifying content, or may be that for filteringcandidates of content to be selected. For example, this may beinformation specifying group specification information to be selected,or may be information representing multiple candidates of groupspecification information to be selected.

Also, it is desirable that when the aforementioned playback period to beplayed next is separated from a certain playback period as previouslydescribed on a timeline, and the aforementioned identificationinformation is included in each playback period existing between acertain playback period as previously described and the playback periodto be played next, the aforementioned selection means identifies thecontent to be selected at the aforementioned playback period to beplayed next by referencing the aforementioned identification informationin order from the playback period immediately before or immediatelyafter a certain playback period as previously described regarding eachplayback period existing between a certain playback period as previouslydescribed and the playback period to be played next.

According to the aforementioned configuration, when the playback periodto be played next is separated from a certain playback period on atimeline, the content to be selected at the playback period to be playednext may still be identified by using the identification information ifthe identification information is included in each playback periodexisting between these playback periods.

For example, the content to be selected at the playback period to beplayed next may be identified by identifying content in order from theplayback period immediately after or immediately before a certainplayback period. Also, for example, when the aforementionedidentification information specifies information filtering the contentto be selected, the information filtering the content to be selected maybe identified in order from the playback period immediately before orimmediately after a certain playback period, the content may be filteredand selected from the information filtering the content to be selectedfor the playback period to be played next.

Also, it is desirable that the aforementioned playback device isprovisioned with a communication unit configured to receive theaforementioned content information on that to be selected, from anexternal device, and the aforementioned selection means selects thecontent using the aforementioned content information on that to beselected which has been received via the aforementioned communicationunit.

According to the aforementioned configuration, as the playback deviceselects content using the content information on that to be selectedreceived via the communication unit, the playback of content may beperformed on the playback device on the basis of the transmitted contentinformation on that to be selected by transmitting the contentinformation on that to be selected to the playback device.

Further, the aforementioned external device may be the server from whichcontent is acquired, or may be another external device. Also, thecontent information on that to be selected may be generated by theaforementioned server, or may be generated by some other device.

Also, other playback devices disclosed in the aforementioned embodimentsacquire and play content selected after referencing content informationon that to be selected including information representing acquirablecontent per playback period of the content, and this playback deviceincludes means configured to acquire information identifying an analysisrange for identifying an analysis range of the content information onthat to be selected for each of the aforementioned playback periods,selection means configured to select content regarding each of theaforementioned playback periods after analyzing the analysis rangeidentified by the aforementioned analysis range identificationinformation acquired by the aforementioned means configured to acquireinformation identifying an analysis range in the aforementioned contentinformation on that to be selected, acquisition means configured toacquire the content selected by the aforementioned selection means, andplayback means configured to play the content acquired by theacquisition means in order of the aforementioned playback periods.

Also, the control method of other playback devices disclosed in theaforementioned embodiments controls the playback device to acquire andplay content selected after referencing content information on that tobe selected including information representing acquirable content perplayback period of the content, and this control method includes a stepfor acquiring information identifying an analysis range for identifyingan analysis range of the content information on that to be selected foreach of the aforementioned playback periods, a selection step forselecting content regarding each of the aforementioned playback periodsafter analyzing the analysis range identified by the aforementionedanalysis range identification information acquired by the aforementionedstep for acquiring information identifying an analysis range in theaforementioned content information on that to be selected, anacquisition step for acquiring the content selected by theaforementioned selection step, and a playback step for playing thecontent acquired by the acquisition step in order of the aforementionedplayback periods.

According to the aforementioned configuration, the analysis rangeidentification information for identifying the analysis range of thecontent information on that to be selected in each playback period isacquired, the analysis range identified by this information is analyzed,the content regarding each playback period is selected, and the selectedcontent is acquired and played in the order of the playback periods.

That is to say, according to the aforementioned configuration, theanalysis range of the content information on that to be selected can benarrower than compared to a case in which content is selected withoutusing analysis range identification information, and so content for eachplayback period is readily selected, and this may be acquired andplayed. Therefore, content depending on the content selected at acertain playback period may be readily selected when transitioning froma certain playback period to the playback period to be played next.

Further, the aforementioned analysis range identification informationmay be any that enables content depending on the content selected at acertain playback period to be readily selected when transitioning from acertain playback period to the playback period to be played next, andnarrows the analysis range of the content information on that to beselected. For example, this may be information specifying attributesshared in the content to be selected at each playback period, or may beinformation specifying a portion of playback periods from a multiple ofthe aforementioned playback periods.

Also, it is preferable that the aforementioned analysis rangeidentification information includes analysis range identificationinformation specifying the analysis range of the aforementioned contentinformation on that to be selected in each of the aforementionedplayback periods, and the aforementioned selection means analyze theanalysis range specified by the aforementioned analysis rangeidentification information, and selects the content for each playbackperiod.

According to the aforementioned configuration, the analysis rangeidentification information includes analysis range identificationinformation specifying the analysis range of the content information onthat to be selected in each playback period, and the analysis rangespecified by the analysis range identification information regarding thecontent information on that to be selected is analyzed.

In this way, the analysis range of the content information on that to beselected is narrowed by performing an analysis at the range specifiedfor each playback period, and the selection of content is simplified.Also, by specifying the analysis range of each playback period in one ofthese so-called analysis range identification information, a consistencyin the selected content may be maintained. For example, the selection ofcontent of the same language at each playback period and others areenabled.

Also, it is desirable that the aforementioned analysis rangeidentification information includes information specifying periods to beplayed for specifying a portion of the playback periods from a pluralityof the aforementioned playback periods, and the aforementioned selectionmeans perform analysis of the playback periods specified by theaforementioned information specifying periods to be played in theaforementioned content information on that to be selected.

According to the aforementioned configuration, the analysis rangeidentification information includes information specifying periods to beplayed for specifying a portion of the playback periods from a pluralityof the playback periods, and analysis is performed on the playbackperiods specified by the information specifying periods to be played inthe content information on that to be selected.

In this way, by filtering the playback periods to be analyzed with theinformation specifying periods to be played, the analysis range of thecontent information on that to be selected is narrowed, and content isreadily selected. Also, a portion of the periods of content may beselectively played.

Further, analysis may be performed using both the information specifyingperiods to be played and the analysis range identification information,and in this case for example, analysis may be performed for the analysisrange specified by the analysis range identification information foreach playback period specified by the information specifying periods tobe played. As a result, the analysis range of the content information onthat to be selected is further narrowed, and the selection of contentbecomes more simplified. Also, a selective playback in which a portionof content having consistency at each playback period is enabled.

Also, it is desirable that the aforementioned playback device isprovisioned with identification information generating means togenerate, as the aforementioned analysis range identificationinformation, information which includes either of informationrepresenting the analysis range when selecting content from the contentinformation on that to be selected including information representingthe content played by the aforementioned playback means, and informationrepresenting the playback position of the content regarding theaforementioned playback means.

By referencing the analysis range identification information generatedaccording to the aforementioned configuration, either of the analysisrange when selecting content from the content information on that to beselected for the content played by the playback means and the playbackposition regarding the playback means may be identified.

Therefore, by referencing the generated analysis range identificationinformation as previously described, the content which has been playedby the playback means may be played from the playback position at whichthe playback means has been playing. Also, the analysis range whenselecting content is filtered by the analysis range identificationinformation, and so the selection of content may be readily performed.

Also, it is desirable that the aforementioned playback device isprovisioned with identification information transmitting meansconfigured to transmit the analysis range identification informationgenerated by the aforementioned analysis range identificationinformation to other devices so that the aforementioned content may beplayed on these devices.

As previously described, by referencing the analysis rangeidentification information generated by the analysis rangeidentification information generating means and analyzing the filteredanalysis range, the content played by the playback means may be playedfrom the playback position at which the playback means has been playing.That is to say, according to the aforementioned configuration, theplayback state regarding the playback means may be easily handed over toanother device.

Here, according to the related art, other than the problems exhibited in[Technical Problem], there has been a problem in which that to be playedcannot be switched to content corresponding to another MPD duringplayback of content based on one MPD. If this kind of switched playbackcould be performed, variations of content playback may be increased, andso this is desirable.

Further, this is not limited to cases when the selection and playback ofcontent is based on the MPD, this problem is also occurs in cases inwhich content is selected after referencing selection informationrepresenting selection candidates of acquirable content.

One object of the present invention is to provide a playback device andso on that may switch that to be played to content corresponding toother selection information during playback of content using contentselection information.

Also, the generating device disclosed in the aforementioned embodimentsgenerates content information on that to be selected includinginformation representing acquirable content per playback period, andthis generating device includes identification information generatingmeans configured to generate identification information for identifyingcontent to be played at the playback period to be played next,corresponding to content selected in a certain playback period, andgenerating means configured to generate the content information on thatto be selected including the identification information generated by theaforementioned identification information generating means.

Also, the control method for the generating device disclosed in theaforementioned embodiments controls the generating device to generatecontent information on that to be selected including informationrepresenting acquirable content per playback period, and this controlmethod includes a step for generating identification information foridentifying content to be played at the playback period to be playednext, corresponding to content selected in a certain playback period,and a step for generating the content information on that to be selectedincluding the identification information generated by the aforementionedstep.

According to the aforementioned configuration, the content informationon that to be selected is generated including the identificationinformation for identifying the content to be played at the playbackperiod to be played next corresponding to the content selected at acertain playback period.

Therefore, the content playback device may select content to be playedin a certain playback period by referencing this content information onthat to be selected, and at the same time, may readily select thecontent to be played at the playback period to be played next inaccordance with the aforementioned identification information.

Also, the recording medium disclosed in the aforementioned embodimentsis a computer-readable recording medium to which the content informationon that to be selected including the information representing acquirablecontent per playback period is recorded, wherein the aforementionedcontent information on that to be selected includes identificationinformation for identifying the content to be played at the playbackperiod to be played next corresponding to the content selected at acertain playback period, and the playback device references theaforementioned content information on that to be selected, selects thecontent to be played in a certain playback period, and at the same time,selects the content to be played at the playback period to be playednext in accordance with the aforementioned identification information.

The playback device that reads out the content information on that to beselected from this recording medium may select the content to be playedin a certain playback period, and at the same time, may readily selectedthe content to be played at the playback period to be played next inaccordance with the aforementioned identification information.

Also, the data structure disclosed in the aforementioned embodiments isthe data structure of the content information on that to be selectedincluding the information representing acquirable content per playbackperiod, and the data structure includes identification information foridentifying content to be played at the playback period to be playednext corresponding to the content selected at a certain playback period,wherein the playback device references the aforementioned contentinformation on that to be selected, selects the content to be played ina certain playback period, and at the same time, selects the content tobe played at the playback period to be played next in accordance withthe aforementioned identification information.

The aforementioned data structure includes the identificationinformation for identifying the content to be selected at the playbackperiod to be played next corresponding to the content selected at acertain playback period, and so the playback device may select thecontent to be played in a certain playback period by using this datastructure, and at the same time, may readily select the content to beplayed at the playback period to be played next in accordance with theaforementioned identification information.

Also, the content selected at a certain playback period as previouslydescribed is a portion of a main content extending over multipleplayback periods, and the content identified by the aforementionedidentification information may be content inserted and playedimmediately before, immediately after, or during the aforementioned maincontent.

According to the aforementioned data structure, the content to beinserted and played immediately before, immediately after, or during themain content extending over multiple playback periods is identified bythe identification information. Therefore, the playback device usingthis data structure inserts and plays other content immediately before,immediately after, or during the aforementioned main content. This isapplicable to a case in which advertising content is inserted into themain content, for example.

The playback device disclosed in the aforementioned embodiments acquiresportions of content selected after referencing the selection informationrepresenting selection candidates for portions of content configuringthe content to be played in order to resolve the aforementioned problem,and plays the acquired portions of content, wherein the aforementionedselection information includes change destination specificationinformation specifying information on change destinations of selectionsrepresenting selection candidates of portions of content configuringcontent with change destinations to be played instead of theaforementioned content to be played, and this playback device isprovisioned with selection means configured to select at least a portionof the portion of content configuring the aforementioned content withchange destinations after referencing the information on changedestinations of selections specified by the aforementioned changedestination specification information during playback of theaforementioned content to be played, and playback means configured toacquire the aforementioned portions of content selected by theaforementioned selection means, and play this instead of theaforementioned content to be played.

The control method of the playback device disclosed in theaforementioned embodiments controls the playback device to acquireportions of content selected after referencing the selection informationrepresenting selection candidates for portions of content configuringthe content to be played in order to resolve the aforementioned problem,and play the acquired portions of content, wherein the aforementionedselection information includes change destination specificationinformation specifying information on change destinations of selectionsrepresenting selection candidates of portions of content configuringcontent with change destinations to be played instead of theaforementioned content to be played, and this control method includes aselection step for selecting at least a portion of the portion ofcontent configuring the aforementioned content with change destinationsafter referencing the information on change destinations of selectionsspecified by the aforementioned change destination specificationinformation during playback of the aforementioned content to be played,and a playback step for acquiring the aforementioned portions of contentselected by the aforementioned selection step, and playing this insteadof the aforementioned content to be played.

According to the aforementioned configuration, the change destinationspecification information specifying the information on changedestinations of selections used for playback of content with changedestinations is included in the selection information used for playbackof content. Also, portions of content (portions of content) with changedestinations are selected using the information on change destinationsof selections specified by the change destination specificationinformation included in this selection information, and the selectedportions of content is acquired and played.

That is to say, according to the aforementioned configuration, thecontent to be played corresponding to the selection information and thecontent with change destinations corresponding to the information onchange destinations of selections are linked by the selectioninformation, and that to be played may be changed from the contentcurrently playing to the content with change destinations.

Also, it is desirable that the aforementioned change destinationspecification information includes playback position specificationinformation for specifying the playback position of the aforementionedcontent with change destinations, wherein the aforementioned selectionmeans select portions of content corresponding to the playback positionspecified by the aforementioned playback position specificationinformation from the portions of content configuring the aforementionedcontent with change destinations.

According to the aforementioned configuration, the change destinationspecification information included playback position specificationinformation specifying the playback position of the content with changedestinations, and the portions of content corresponding to the playbackposition specified by this information is selected. As a result, thecontent to be played is changed from the content currently playing tothe portions of content regarding the content with change destinationscorresponding to the aforementioned playback position. That is to say,according to the aforementioned configuration, playback of the contentwith destinations from the playback position specified by the playbackposition specification information is enabled.

Also, it is desirable that the aforementioned selection informationincludes the aforementioned playback position specification informationspecifying the playback position depending on the playback period ineach playback period of the aforementioned content, wherein theaforementioned selection means select the portions of contentcorresponding to the playback position specified by the playbackposition specification information corresponding to the playback periodof the aforementioned content played by the aforementioned playbackmeans form the portions of content configuring the aforementionedcontent with change destinations.

According to the aforementioned configuration, portions of contentcorresponding to the playback position specified by the playbackposition specification information corresponding to the playback periodof the content currently playing is selected from the portions ofcontent configuring the content with change destinations. Therefore, thecontent with change destinations may be played from the playbackposition depending on the playback period of the content currentlyplaying.

Also, it is desirable that the aforementioned content and the portionsof content configuring the content with change destinations are bothconfigured as multiple segments, wherein the aforementioned selectioninformation includes identification information for identifying thesegments configuring the aforementioned content, the aforementionedinformation on change destinations of selections includes identificationinformation for identifying the segments configuring the aforementionedcontent with change destinations, the aforementioned playback positionspecification information is information representing the segments ofthe content with change destinations including identificationinformation corresponding to the segments of the aforementioned contentplayed by the aforementioned playback means, and the aforementionedselection means select the segments represented by the aforementionedplayback position specification information.

According to the aforementioned configuration, the playback position isspecified by the segments configuring the portions of content regardingthe content with change destinations. Therefore, the playback positionmay be finely specified as compared to a case in which the playbackposition is specified at the portions of content configuring the contentwith change destinations.

Also, it is desirable that the aforementioned content with changedestinations is content in which the same contents of the aforementionedcontent has different playback speeds, wherein identificationinformation included in the aforementioned selection information andidentification information included in the aforementioned information onchange destinations of selections are set so that the segmentscorresponding to the identification information are the same contentswith different playback speeds.

According to the aforementioned configuration, the content with changedestinations is content in which the same contents of the aforementionedcontent has different playback speeds, and the identificationinformation included in the aforementioned selection information and theidentification information included in the aforementioned information onchange destinations of selections are set so that the segmentscorresponding to the identification information are the same contentswith different playback speeds.

Therefore, the segments in which the contents of the content currentlyplaying until the time when changing to the content with changedestinations are the same and having different playback speeds areplayed. That is to say, according to the aforementioned configuration, atrick play is enabled in which the playback speed changes duringplayback of the content.

Further, the aforementioned playback device and the aforementionedgenerating device may be implemented by a computer, and in this case, byoperating the computer as each of the means of the aforementionedplayback device and the aforementioned generating device, a controlprogram for implementing the aforementioned playback device and theaforementioned generating device on a computer, and a computer-readablerecording medium for recording to this is within the scope of thepresent invention.

INDUSTRIAL APPLICABILITY

The present invention may be used in a playback device or similarplaying content acquired via a network.

REFERENCE SIGNS LIST

-   -   1 client (playback device)    -   2 server (generating device)    -   12 client communication unit (communication unit)    -   13 content selection unit (selection means, means configured to        acquire analysis range identification information)    -   14 request execution unit (acquisition means)    -   15 content playback unit (playback means, means configured to        generate analysis range identification information,        identification information transmitting means)    -   23 description information transmitting unit (identification        information generating means, generating means)    -   25 content    -   26 description information (content information on that to be        selected, information on change destinations of selections)

The invention claimed is:
 1. A playback device comprising: selection circuitry that selects content to be played at each playback period from selection candidates, each respectively represented by at least one of: first candidate information identified using first identification information and second candidate information identified using second identification information, acquisition circuitry that acquires the content selected by the selection circuitry; and playback circuitry that plays the content acquired by the acquisition circuitry; wherein the playback device obtains and plays the content selected after referencing content information including information representing acquirable content in each playback period, and in each playback period: at least one of the first candidate information representing one or a plurality of content is included in the content information, the first identification information is correlated with each of the at least one of the first candidate information, at least one of the second candidate information, representing one or a plurality of the first candidate information, is included in the content information, the second identification information is correlated with each of the at least one of the second candidate information, the second identification information is set such that content with continuity between a current playback period and a next playback period is selected, by selecting content using the second identification information; and the second candidate information correlated with the second identification information of a same value between the current playback period and the next playback period. 